Top 150 System design Interview Questions
Practice the most frequently asked system design interview questions. Each question includes expert tips, sample answers, and AI-powered practice.
Discuss ACID vs. BASE properties
Interviewers at Microsoft ask this to evaluate your ability to make trade-off decisions in distributed systems. They want to see if you understand that consistency isn't binary but a spectrum. This question tests whether you can justify architectural choices based on business requirements rather than blindly adhering to one paradigm.
Discuss Serverless Functions vs. Containers (FaaS vs. CaaS)
Interviewers at Apple ask this to evaluate your ability to make pragmatic architectural trade-offs rather than just listing features. They want to see if you understand the operational implications of FaaS versus CaaS, specifically regarding cost efficiency, latency sensitivity, and resource management in large-scale distributed systems.
Design a User Login and Authentication Service
Interviewers at Apple ask this to evaluate your ability to balance user convenience with rigorous security standards. They assess your understanding of cryptographic principles, your awareness of modern threat vectors like CSRF and brute force attacks, and your capacity to design scalable systems that handle sensitive user data without compromising privacy.
Design a Simple API Throttling Mechanism
Interviewers at IBM ask this to assess your ability to balance system reliability with resource protection. They evaluate whether you understand the trade-offs between implementation simplicity and accuracy in rate limiting, specifically testing your grasp of concurrency issues and data consistency when managing request counts without distributed coordination.
Discuss Microservices vs. Monolith Architecture
Interviewers at Meta ask this to assess your ability to make trade-off decisions rather than just memorizing definitions. They want to see if you understand that architecture is context-dependent, evaluating your capacity to weigh scalability needs against operational complexity. This question reveals whether you can align technical choices with business goals and organizational maturity.
Design a Basic Messaging Queue Service
Interviewers ask this to assess your ability to translate abstract distributed systems concepts into concrete database interactions. At Uber, where reliability is paramount, they evaluate if you understand the trade-offs of using a SQL database for queuing versus dedicated message brokers like Kafka or RabbitMQ.
Discuss Data Replication Techniques (Primary-Secondary)
Interviewers at Oracle ask this to verify your grasp of distributed database consistency models. They specifically evaluate your ability to balance data durability against system availability and latency. Understanding the trade-offs between synchronous and asynchronous replication demonstrates whether you can design systems that meet specific business RPO and RTO requirements rather than just knowing definitions.
Design a System for Storing User Preferences
Interviewers ask this to evaluate your ability to balance scalability with low-latency access for high-volume data. They specifically want to see if you understand the trade-offs between document databases like MongoDB and in-memory caches, ensuring you can handle billions of frequently changing records without compromising Apple's user experience standards.
Discuss Columnar vs. Row-Oriented Databases
Interviewers at Oracle ask this to assess your fundamental understanding of storage engines and data modeling. They want to see if you can distinguish between OLTP and OLAP workloads, ensuring you select the right architecture for specific business needs rather than defaulting to a single database type.
Design an API Gateway
Interviewers at Salesforce ask this to evaluate your ability to design scalable, secure microservices architectures. They specifically assess whether you understand how to centralize cross-cutting concerns like authentication and rate limiting without coupling them to business logic. This question tests your capacity to balance performance with maintainability in a high-volume enterprise environment.
Design a Pastebin Service
Interviewers ask this to evaluate your ability to balance simplicity with scalability while addressing specific constraints like data expiration and input validation. They want to see if you can design a system that handles malicious inputs efficiently without over-engineering, reflecting Uber's focus on robust, cost-effective infrastructure for high-traffic services.
Design a Simple API Documentation Service
Interviewers at Salesforce ask this to evaluate your ability to design scalable, automated infrastructure for developer productivity. They specifically want to see how you handle the complexity of ingesting metadata from thousands of microservices while ensuring consistency, versioning, and rapid updates without manual intervention.
Design a URL Shortening Service (TinyURL)
Google asks this to evaluate your ability to balance trade-offs between simplicity and scalability. They specifically want to see if you can design a stateless, high-throughput system that handles massive write loads for shortening while maintaining sub-millisecond read latency for millions of users globally.
Discuss Optimistic vs. Pessimistic Locking
Amazon interviewers ask this to evaluate your ability to balance system throughput against data consistency in distributed environments. They specifically test if you understand the trade-offs between concurrency control strategies, ensuring you can select the right mechanism based on conflict probability and read/write patterns rather than defaulting to a single approach.
Design a Dedicated Health Check Service
Interviewers at Uber ask this to evaluate your ability to design resilient, self-healing distributed systems. They specifically want to see if you understand the critical role of observability in high-scale environments and can distinguish between proactive monitoring strategies versus reactive metrics.
Design a Simple Blog Platform (WordPress)
Adobe asks this to evaluate your ability to balance simplicity with scalability for content-heavy applications. They specifically want to see if you understand how to structure data efficiently using normalization while implementing performance layers like caching and CDNs to handle traffic spikes without over-engineering the solution.
Design a Shopping Cart Service
Interviewers ask this to evaluate your ability to balance trade-offs between consistency, availability, and latency in a stateless environment. Specifically, they test if you understand Amazon's customer-obsessed need for instant cart updates while handling high concurrency without data loss.
Design a System to Handle Retries and Backoff
Interviewers at Salesforce ask this to evaluate your understanding of distributed system resilience and your ability to prevent cascading failures. They specifically want to see if you grasp how transient errors differ from permanent ones, and whether you can design a mechanism that protects backend services from being overwhelmed by retry storms during outages.
Design a Payment Processing System
Interviewers at Uber ask this to evaluate your ability to design distributed systems where financial integrity is non-negotiable. They specifically assess your understanding of ACID properties, how to prevent double-spending through idempotency, and your strategy for handling partial failures using two-phase commits. The goal is to see if you can balance high availability with strict consistency in a real-world, high-throughput environment.
Design a System for Real-Time Fleet Management
Interviewers at Uber ask this to evaluate your ability to architect scalable, low-latency systems under extreme concurrency. They specifically test your grasp of real-time data ingestion pipelines, dynamic pathfinding algorithms for millions of nodes, and trade-offs between consistency and availability in a distributed environment.
Design a Key-Value Store (Distributed Cache)
Amazon interviewers ask this to evaluate your ability to design scalable, fault-tolerant systems under the CAP theorem constraints. They specifically test your grasp of distributed consistency, partitioning strategies like consistent hashing, and failure recovery mechanisms. This question reveals if you can balance trade-offs between availability and latency while adhering to Amazon's leadership principles of customer obsession and inventing simply.
Design a Real-time Auction Bidding System
Meta evaluates this question to assess your ability to architect distributed systems under extreme concurrency. They specifically look for how you handle micro-latency requirements in high-frequency trading scenarios, manage race conditions when multiple users bid simultaneously, and ensure fairness by preventing starvation of lower bids while maintaining system consistency.
Design an Online Game Backend (Multiplayer)
Microsoft asks this to evaluate your ability to balance performance with security in distributed systems. They specifically test if you understand the critical trade-offs between client-side prediction and server authority, as well as your strategy for handling network jitter and malicious actors in real-time environments.
Design a System for Monitoring Service Mesh (Istio/Linkerd)
Interviewers at IBM ask this to evaluate your ability to design distributed systems with high reliability and observability. They specifically test your understanding of sidecar patterns, control plane separation, and how to implement non-intrusive monitoring for complex microservice interactions like circuit breaking and latency tracking.
Design a Low-Latency Trading Bot API
Interviewers ask this to evaluate your ability to design systems where time is the primary constraint. They specifically test your understanding of hardware-software co-design, kernel bypass techniques, and collocation strategies. The goal is to see if you can prioritize microsecond latency over scalability or ease of maintenance, a critical skill for high-frequency trading environments.
Explain the Raft Consensus Algorithm
Interviewers at Meta ask this to evaluate your grasp of distributed system reliability and your ability to reason about complex state machine replication. They specifically test if you understand how to achieve consistency in the presence of network partitions and node failures, which is critical for their infrastructure like F5 or internal data stores.
Design a Fraud Detection System for Reviews/Ratings
Amazon asks this to evaluate your ability to balance system scalability with data integrity under adversarial conditions. They specifically test if you can design a real-time anomaly detection pipeline that distinguishes between organic user behavior and coordinated bot networks, reflecting their customer obsession principle of protecting the marketplace ecosystem.
Design a Public Transit Monitoring System
Interviewers at Uber ask this to evaluate your ability to architect real-time systems under latency constraints. They specifically assess how you handle high-velocity sensor ingestion, manage data consistency for location tracking, and design scalable prediction models that account for dynamic traffic variables while maintaining system reliability.
Design an IoT Sensor Data Ingestion Pipeline
Interviewers at Tesla ask this to evaluate your ability to architect systems balancing extreme scale with strict latency requirements. They specifically test your judgment on edge versus cloud trade-offs, as Tesla vehicles must operate safely even when disconnected from the network. The question assesses your capacity to design for data loss resilience and your understanding of real-time constraints in safety-critical environments.
Design a Voice/Audio Processing Pipeline
Spotify asks this to evaluate your ability to architect scalable, low-latency audio systems under heavy load. They specifically assess your understanding of streaming architectures, chunking strategies for variable-length files, and how to handle asynchronous processing pipelines efficiently without blocking I/O operations.
Design an Image Moderation Service (NSFW Detection)
Interviewers at Meta ask this to evaluate your ability to balance high-scale system reliability with critical safety requirements. They specifically assess how you handle asynchronous processing for media-heavy workloads, manage trade-offs between model latency and accuracy, and design robust human-in-the-loop review queues for edge cases that automated systems miss.
Design a Chat System (WhatsApp/WeChat)
Meta asks this to evaluate your ability to architect real-time systems handling millions of concurrent connections. They specifically test your understanding of WebSocket persistence, message delivery guarantees like at-least-once semantics, and how to manage state consistency across distributed servers for both private and group chats without data loss.
Design a Spam Filter for Email/Messaging
Interviewers at Microsoft ask this to evaluate your ability to architect scalable, real-time systems while balancing accuracy with latency. They specifically test your understanding of the trade-offs between static rule-based filtering and dynamic machine learning models, as well as your capacity to design feedback loops that adapt to evolving spam tactics without human intervention.
Design an Identity Management System (OAuth/SSO)
Interviewers at Microsoft ask this to evaluate your ability to architect secure, scalable identity infrastructure critical for their ecosystem. They assess deep understanding of OAuth 2.0 and OIDC standards, token lifecycle management, and the trade-offs between security and user experience in distributed systems.
Design a Video Conferencing Service (Zoom)
Meta evaluates candidates on their ability to architect scalable, low-latency real-time systems. This question specifically tests your understanding of WebRTC constraints, the trade-offs between SFU and MCU architectures for group calls, and your capacity to optimize bandwidth and jitter management under high-concurrency scenarios typical of Meta's massive user base.
Design a Geofencing Service
Interviewers at Uber ask this to evaluate your ability to design scalable spatial systems handling millions of concurrent mobile clients. They specifically test your knowledge of geospatial indexing, trade-offs between accuracy and latency, and how to optimize database queries for high-frequency location updates without overwhelming backend resources.
Design a Peer-to-Peer File Sharing System (BitTorrent)
Interviewers at Netflix ask this to evaluate your ability to design distributed systems that prioritize high availability and scalability under massive load. They specifically test if you understand how to handle peer churn, optimize bandwidth usage through chunking, and implement efficient discovery mechanisms without relying on a single point of failure.
Design a System for Geo-Distributed Data Storage
Interviewers at Apple ask this to evaluate your ability to balance strong consistency guarantees with global latency requirements. They specifically test your understanding of the CAP theorem in a real-world context, focusing on how you handle multi-master write conflicts and eventual consistency patterns across continents without compromising user experience or data integrity.
Design a Hotel Booking System (Airbnb/Booking.com)
Interviewers at Airbnb ask this to evaluate your ability to handle high-concurrency distributed systems where data consistency is critical. They specifically want to see how you manage race conditions during simultaneous bookings, design efficient indexing for complex geo-spatial filtering, and ensure inventory integrity without blocking user experience under heavy load.
Design a System for Storing and Querying Logs (Splunk)
Interviewers at Microsoft ask this to evaluate your ability to design high-throughput data ingestion pipelines and optimize search latency for unstructured data. They specifically assess your understanding of the trade-offs between write speed, storage efficiency, and query performance in distributed systems, a critical skill for maintaining Azure Monitor and similar telemetry platforms.
Design a Fraud Detection System
Interviewers at Stripe ask this to evaluate your ability to balance extreme low-latency requirements with high-accuracy machine learning in a distributed environment. They specifically test if you understand the nuances of real-time data streaming, feature engineering for fraud patterns, and how to manage the critical trade-off between false positives that frustrate users and false negatives that cost money.
Design a Compliance Monitoring System (GDPR/HIPAA)
Salesforce evaluates this question to assess your ability to architect secure, scalable systems while navigating complex regulatory landscapes like GDPR and HIPAA. They specifically test your understanding of data sovereignty, real-time threat detection, and how to implement immutable audit trails that satisfy strict legal requirements without compromising system performance.
Design a Ride-Hailing Service (Uber/Lyft)
Interviewers ask this to evaluate your ability to handle massive scale geospatial data challenges. They specifically test your knowledge of spatial indexing algorithms like Geohash, your understanding of real-time latency constraints in high-frequency matching systems, and your capacity to balance consistency with availability when estimating ETAs for millions of concurrent users.
Design a Distributed File System (HDFS/S3)
Amazon asks this to evaluate your ability to design systems that prioritize high availability and durability under failure conditions. They specifically test if you understand the trade-offs between consistency, partition tolerance, and availability in a distributed environment. The question probes your grasp of how massive scale data is managed without single points of failure, a core tenet of Amazon's infrastructure.
Design a Distributed Transaction System
Interviewers at Stripe ask this to evaluate your ability to balance strong consistency with high availability in financial systems. They want to see if you understand that distributed transactions are not just about protocols, but about managing eventual consistency, handling partial failures gracefully, and making architectural trade-offs that align with real-world payment reliability requirements.
Design a Stock Exchange Matching Engine
Interviewers at Stripe ask this to evaluate your ability to design low-latency, high-concurrency systems under strict consistency constraints. They specifically test your grasp of data structures like heaps for order matching, your understanding of race conditions in distributed ledgers, and your capacity to prioritize performance metrics critical to financial infrastructure.
Design a Cloud Storage Service (Dropbox/Google Drive)
Microsoft evaluates this question to assess a candidate's ability to design distributed systems that handle data consistency across unreliable networks. They specifically look for deep understanding of eventual consistency models, conflict resolution strategies like CRDTs or vector clocks, and the trade-offs between latency and strong consistency in large-scale synchronization.
Design the YouTube Video Streaming Service
Interviewers at Netflix ask this to evaluate your ability to architect high-scale, low-latency systems under extreme load. They specifically test your understanding of the trade-offs between storage costs, encoding efficiency, and viewer experience. The goal is to see if you can design a solution that handles millions of concurrent streams while maintaining seamless adaptive bitrate streaming across diverse network conditions.
Design a URL Shortener
Meta asks this to evaluate your ability to architect scalable, distributed systems under constraints. They specifically test your understanding of hash collision handling, database sharding strategies for massive read-heavy workloads, and how to balance latency against consistency when billions of requests hit the service daily.
Design a Distributed File Locking System
Interviewers ask this to evaluate your ability to handle distributed consistency, race conditions, and fault tolerance in high-concurrency environments. They specifically want to see if you understand the CAP theorem trade-offs when designing coordination services like ZooKeeper. The question tests your capacity to translate theoretical consensus algorithms into a practical, production-grade locking mechanism that prevents data corruption across a cluster.
Design a Type-Ahead with Spell Check
Interviewers at Uber ask this to evaluate your ability to balance strict latency requirements with complex algorithmic logic. They want to see if you can design a system that handles real-time user input while efficiently calculating edit distances without blocking the main thread, reflecting Uber's need for instant, reliable navigation and search experiences.
Design a Graph Database Service (Neo4j)
Interviewers at Meta ask this to evaluate your ability to model complex, interconnected data where traditional relational databases fail. They specifically test your understanding of graph traversal algorithms, index strategies for high-cardinality relationships, and your capacity to design systems optimized for deep path queries common in social networks and recommendation engines.
Design a Collaborative Editing System (Google Docs)
Interviewers at Google ask this to evaluate your ability to design distributed systems that handle high concurrency without data loss. They specifically test your understanding of Operational Transformation (OT) or CRDTs, assessing whether you can manage conflict resolution in real-time environments where network latency causes simultaneous edits.
Design a Geo-Distributed Leaderboard with Strong Consistency
Google asks this to evaluate your ability to navigate the CAP theorem trade-offs in a real-world scenario. They specifically test if you understand that strong consistency globally often conflicts with low latency, and whether you can architect a solution like single-region write dominance or conflict-free replicated data types that prioritizes data integrity over availability when required by business logic.
Design a Digital Rights Management (DRM) System
Netflix asks this to evaluate your ability to balance strict security requirements with seamless user experience at massive scale. They need to see if you can architect a system that prevents piracy while ensuring low-latency playback for millions of concurrent users. The question tests your grasp of cryptographic protocols, key distribution strategies, and handling edge cases like license revocation without disrupting active streams.
Design a System for Real-Time Facial Recognition
Apple asks this to evaluate your ability to balance strict latency requirements with high-accuracy constraints in privacy-sensitive environments. They want to see if you can architect a pipeline that handles massive video throughput while efficiently managing vector similarity search without compromising user data security or model inference speed.
Design a Video Recommendation Engine (Short Form)
Interviewers ask this to evaluate your ability to architect high-throughput, low-latency systems handling massive scale. They specifically test your understanding of the two-stage funnel (candidate generation vs. ranking), real-time feature processing for short-form content, and how to balance personalization with exploration in a cold-start scenario.
Design a System for Identity Verification (KYC)
Interviewers at Stripe ask this to evaluate your ability to balance high-scale system architecture with critical compliance and security requirements. They specifically test if you can design a robust pipeline for document ingestion, OCR processing, and third-party API orchestration while prioritizing data privacy, auditability, and fault tolerance in a financial context.
Design an Enterprise Resource Planning (ERP) System
Interviewers at IBM ask this to evaluate your ability to architect scalable, multi-tenant enterprise solutions. They specifically assess how you handle data consistency across disparate modules like Finance and Supply Chain, manage complex integrations, and prioritize non-functional requirements such as security and compliance in a legacy-heavy environment.
Design a Service for Real-time Analytics
Amazon asks this to evaluate your ability to design scalable, fault-tolerant systems that handle massive throughput while meeting strict latency requirements. They specifically test your understanding of trade-offs between batch and stream processing, and whether you can architect a solution aligned with their customer-obsession for real-time insights without over-engineering the infrastructure.
Design a Recommendation System (Netflix)
Interviewers at Netflix ask this to evaluate your ability to balance business impact with technical depth. They specifically test if you understand how to handle massive-scale data, the trade-offs between cold-start problems and personalization accuracy, and your capacity to design a robust, low-latency pipeline that directly influences user retention.
Design a System to Detect Plagiarism
Interviewers at Google ask this to evaluate your ability to handle massive-scale data problems where exact matching is computationally impossible. They specifically test your knowledge of probabilistic algorithms like MinHash and LSH, your capacity to balance precision with recall, and your skill in designing distributed systems that can process millions of documents efficiently within strict latency constraints.
Design a System for Data Sharding and Indexing
Interviewers at Amazon ask this to evaluate your ability to design scalable, automated data architectures that handle massive growth without human intervention. They specifically assess your understanding of consistency models, failure handling during shard rebalancing, and the trade-offs between indexing latency and throughput in a distributed environment.
Design a Time Series Database (TSDB)
Tesla evaluates this question to assess your ability to architect systems for high-velocity IoT data from vehicles. They specifically test your understanding of write-heavy workloads, efficient compression algorithms like Delta-of-Delta or Gorilla, and time-based indexing strategies that enable rapid aggregation without sacrificing storage costs.
Design a Distributed Search Service (Elasticsearch)
Interviewers at Amazon ask this to evaluate your ability to architect systems that handle massive scale while maintaining low latency. They specifically test your understanding of how distributed architectures manage data consistency, fault tolerance, and query performance when dealing with billions of documents.
Design a Distributed Semaphore
Interviewers at Stripe ask this to evaluate your ability to handle distributed consensus and race conditions in high-throughput financial systems. They specifically test your understanding of eventual consistency, leader election, and failure scenarios like network partitions or node crashes. The goal is to see if you can design a solution that guarantees mutual exclusion without creating a single point of failure.
Design a Dynamic Pricing Engine
Interviewers at Uber ask this to evaluate your ability to balance complex algorithmic logic with real-world business constraints. They specifically test your understanding of how machine learning models integrate into high-throughput systems, your awareness of the risks associated with price volatility, and your strategy for validating model performance through rigorous A/B testing before full deployment.
Design a System for Handling Big Data Joins
Interviewers at Spotify ask this to evaluate your ability to architect scalable solutions for massive datasets, a daily reality in music streaming. They assess your understanding of distributed computing trade-offs, specifically how to handle skew and memory constraints during joins. The goal is to see if you can design systems that maintain low latency while processing petabytes of user activity and metadata efficiently.
Design a Machine Learning Model Deployment Service (MLOps)
Netflix evaluates candidates on their ability to design resilient, scalable MLOps pipelines that support high-velocity content personalization. Interviewers specifically test your understanding of the trade-offs between speed and safety in model updates, ensuring you can maintain service reliability while continuously improving recommendation accuracy without causing user-facing disruptions.
Design a Ticketing Master System
Uber asks this to evaluate your ability to design systems handling extreme concurrency where data integrity is non-negotiable. They specifically test if you can architect a solution that prevents double-booking during flash sales, balancing strict ACID compliance with high availability and low latency under massive traffic spikes.
Design a Distributed Job Scheduler (Cron Service)
Interviewers at Microsoft ask this to evaluate your ability to design fault-tolerant, scalable systems under constraints. They specifically test your understanding of distributed consensus, idempotency, and how to handle clock skew across thousands of nodes while ensuring exactly-once execution semantics for critical workloads.
Design a CDN Edge Caching Strategy
Interviewers at Amazon ask this to evaluate your ability to balance performance, cost, and data consistency in distributed systems. They specifically test your understanding of edge computing trade-offs, your grasp of cache invalidation strategies, and your capacity to design solutions that handle real-world variability like regional user behavior without over-engineering.
Design a System for Monitoring Service Health
Interviewers at Salesforce ask this to evaluate your ability to design scalable, reliable monitoring systems for complex microservice architectures. They specifically assess your understanding of data collection strategies, trade-offs between pull and push models, and how to handle high-volume metrics without overwhelming the system or losing critical health signals during outages.
Design a System to Handle Retries and Dead Letter Queues (DLQ)
Interviewers at Cisco ask this to evaluate your ability to design resilient distributed systems that handle transient failures gracefully. They specifically want to see if you understand the trade-offs between data durability and system availability, and whether you can architect a solution that prevents message loss while avoiding infinite retry loops that could overwhelm downstream services.
Design a System for Monitoring API Latency
Interviewers at Salesforce ask this to evaluate your ability to balance system reliability with cost efficiency. They specifically want to see if you understand that collecting every data point for thousands of endpoints is unsustainable. This question tests your judgment in choosing between sampling strategies and full-data collection while ensuring critical alerts trigger without overwhelming infrastructure.
Design a Subscription Management Service
Interviewers at Netflix ask this to evaluate your ability to design resilient, stateful systems that handle financial data with high consistency. They specifically look for your understanding of idempotency in payment processing, handling edge cases like network failures during billing, and ensuring data integrity across distributed services without losing revenue or customer trust.
Design a Simple ETL Pipeline
Interviewers at Netflix ask this to evaluate your ability to design robust, scalable data systems that prioritize reliability and data integrity. They specifically test your understanding of idempotency to prevent duplicate records in high-volume environments, your approach to handling dirty production data, and your strategy for scheduling incremental loads without impacting source system performance.
Design an API Caching Layer
Apple evaluates system design candidates on their ability to balance performance with data consistency in distributed systems. This question specifically tests your understanding of trade-offs between read throughput and write latency, ensuring you can architect a solution that scales without compromising the integrity of user data or causing stale information issues.
Design a Notification Service (Push/SMS/Email)
Interviewers at Meta ask this to evaluate your ability to design scalable, fault-tolerant distributed systems under high load. They specifically assess how you balance throughput with delivery guarantees when handling millions of daily events. The question tests your understanding of asynchronous processing, message broker selection, and strategies for managing partial failures without blocking the entire system.
Design an Autocomplete/Type-Ahead Service
Amazon asks this to evaluate your ability to balance trade-offs between latency, storage, and accuracy in a high-scale environment. They specifically test if you understand how Tries optimize prefix matching compared to linear scans. The question probes your capacity to design for the 'Customer Obsession' principle by ensuring suggestions appear instantly as users type, directly impacting conversion rates on platforms like Amazon.com.
Design a Real-Time Commenting System
Meta interviewers ask this to evaluate your ability to balance high read-throughput with low-latency writes in a globally distributed environment. They specifically test if you can design for real-time consistency using caching layers and pub/sub mechanisms while handling write amplification common in social feeds.
Design a Simple Search Engine
Interviewers ask this to evaluate your ability to design scalable data systems and understand the core mechanics of information retrieval. They specifically assess your knowledge of inverted indexes, document tokenization strategies, and query processing efficiency. For Google, this tests your capacity to balance trade-offs between indexing speed, storage cost, and search latency in a distributed environment.
Design an Ad Click Tracking Service
Interviewers at Microsoft ask this to evaluate your ability to design systems that handle massive write throughput while prioritizing availability over strict consistency. They want to see if you can balance trade-offs like partitioning strategies, caching layers, and eventual consistency models when tracking billions of daily events without data loss.
Design an Online Polling Service
Interviewers at Meta ask this to evaluate your ability to handle extreme scale and read-heavy workloads typical of their social products. They specifically test your capacity to distinguish between transient write phases during poll creation and sustained read phases for result aggregation, ensuring you can justify database choices like Redis for caching versus SQL for durability under massive concurrent traffic.
Design an Image Hosting Service (Instagram/Flickr)
Interviewers at Meta ask this to evaluate your ability to architect scalable systems handling massive unstructured data. They specifically test your understanding of storage trade-offs, the critical role of CDNs in latency reduction, and how to design efficient image processing pipelines that decouple heavy compute from user requests.
Design a Highly Available DNS Service
Interviewers ask this to evaluate your ability to design resilient distributed systems that handle massive scale. They specifically test your understanding of DNS protocols, caching strategies like TTL, and how to ensure low-latency global availability through geographic redundancy without creating single points of failure.
Design a System for Feature Flags/Toggles
Apple interviewers ask this to evaluate your ability to design systems that balance extreme reliability with granular control. They specifically want to see if you can architect a solution that ensures zero downtime during feature rollouts while handling high-scale traffic without adding latency. The question tests your understanding of consistency models, data partitioning strategies for user targeting, and how to manage the complexity of dynamic configuration across global services.
Design a Data Lakehouse Architecture
Interviewers at Oracle ask this to evaluate your ability to synthesize modern data trends into practical architectures. They specifically test if you understand the convergence of unstructured lake flexibility and structured warehouse governance. The question assesses your knowledge of ACID transactions, schema evolution, and tool selection like Delta Lake or Hudi in a cloud-native context.
Design an Email Service (SMTP/Sending)
Meta asks this to evaluate your ability to design highly available, distributed systems that handle massive scale. They specifically test your understanding of reliability patterns like idempotency and backoff strategies, not just basic SMTP protocols. The goal is to see if you can balance throughput with deliverability while managing complex state transitions in a distributed environment.
Design a Distributed Unique ID Generator (Snowflake)
Interviewers at Google ask this to evaluate your ability to design scalable systems under strict constraints. They specifically test your understanding of clock synchronization, collision avoidance in distributed environments, and how to handle node failures without compromising ID uniqueness or monotonicity.
Design a Server-Side Rendering (SSR) System
Interviewers ask this to evaluate your ability to balance performance, consistency, and user experience in modern web architectures. Specifically, they assess how you handle the critical path of rendering, manage data flow between server and client, and optimize for Core Web Vitals like LCP while ensuring seamless state synchronization during hydration.
Design an Asynchronous Task Processing System
Apple evaluates this question to assess your ability to design scalable, resilient distributed systems that handle non-blocking operations. They specifically look for your understanding of decoupling producers from consumers, managing worker concurrency, and ensuring data integrity through persistent storage without sacrificing system availability.
Design a Multi-Region Cloud Deployment
Interviewers at Microsoft ask this to evaluate your ability to architect resilient, globally distributed systems. They specifically test your understanding of trade-offs between consistency and availability in multi-region setups, your knowledge of cloud-native patterns like active-active vs. active-passive, and your strategic thinking regarding latency reduction and disaster recovery planning.
Design a URL Click Tracking Service
Interviewers at Cisco ask this to evaluate your ability to balance high-throughput write performance with read consistency in distributed systems. They specifically want to see if you understand trade-offs between strong consistency and eventual consistency when handling massive click volumes, as well as your skill in selecting appropriate storage solutions like key-value stores or stream processing pipelines.
Design a System for Customer Relationship Management (CRM)
Interviewers at Salesforce ask this to evaluate your ability to architect complex, multi-tenant systems that balance data isolation with shared resources. They specifically test your understanding of core CRM domains like sales and service while assessing how you handle scalability, consistency, and the unique challenges of a platform serving millions of global users.
Discuss Event Sourcing Architecture
Interviewers at Microsoft ask this to evaluate your ability to design systems that require high auditability, complex state reconstruction, and scalability. They specifically want to see if you understand the trade-offs between consistency, performance, and data integrity when choosing an immutable log over traditional CRUD databases for financial or critical business logic scenarios.
Design a Centralized Configuration Management System
Interviewers at Tesla ask this to evaluate your ability to design resilient, real-time distributed systems essential for managing vehicle firmware and fleet configurations. They specifically assess your understanding of consistency models, conflict resolution strategies, and how to ensure zero-downtime updates across a massive scale where safety is paramount.
Design a Geo-Spatial Indexing System
Interviewers at Apple ask this to evaluate your ability to balance theoretical computer science with practical engineering constraints. They specifically test if you understand how to handle massive datasets efficiently while maintaining low latency for location-based services, a core competency for their Maps and Find My ecosystems.
Design a Stock Ticker/Price Feed Service
Interviewers at Stripe ask this to evaluate your ability to design high-throughput, low-latency systems under extreme scale. They specifically test your understanding of connection multiplexing and fan-out protocols like WebSockets, ensuring you can balance real-time data consistency with the massive concurrency required by financial infrastructure.
Design the Twitter News Feed
Interviewers ask this to evaluate your ability to balance scalability with real-time performance in high-traffic systems. They specifically test your understanding of fan-out patterns, how to handle hot spots like celebrity users without crashing the system, and your capacity to prioritize trade-offs between consistency and availability.
Design a Distributed Cron/Scheduler Service
Interviewers at Google ask this to evaluate your ability to design resilient distributed systems under failure conditions. They specifically assess how you handle race conditions, ensure exactly-once execution semantics, and manage leader election without a single point of failure. This question reveals if you can balance consistency with availability when coordinating tasks across unreliable network nodes.
Design a System for Data De-Duplication
Interviewers at LinkedIn ask this to evaluate your ability to balance computational efficiency with data accuracy in distributed environments. They specifically want to see if you understand how to handle massive scale without O(N^2) comparisons, and whether you can apply probabilistic techniques like MinHash or locality-sensitive hashing to solve real-world duplicate detection problems.
Design a Digital Asset Management (DAM) System
Adobe asks this to evaluate your ability to architect scalable storage solutions for high-value creative assets. They specifically assess your understanding of metadata indexing strategies, efficient version control mechanisms for large binaries, and how to balance latency with consistency in a distributed environment typical of their Creative Cloud ecosystem.
Design an Inventory Management System
Amazon asks this to evaluate your ability to design scalable systems that handle high concurrency and data consistency. They specifically test if you understand distributed database challenges like race conditions when millions of users update stock simultaneously. The goal is to see if you can prioritize atomicity and fault tolerance over simple CRUD operations.
Design a Distributed Caching System (Memcached)
Interviewers at Google ask this to evaluate your ability to design scalable, high-performance systems under constraints. They specifically test your understanding of consistency models, data partitioning strategies like consistent hashing, and failure handling in distributed environments. The goal is to see if you can balance latency against complexity while ensuring the system remains available during node failures.
Design a News Aggregator (Google News)
Interviewers ask this to evaluate your ability to architect scalable distributed systems handling massive unstructured data. They specifically assess your understanding of web crawling constraints, real-time deduplication strategies using hashing or embeddings, and clustering algorithms for grouping similar stories. At Google, they also look for your capacity to balance trade-offs between consistency, latency, and cost in a high-throughput environment.
Design a System for Live Stream Polling/Reactions
Meta interviewers ask this to evaluate your ability to architect high-throughput, low-latency systems under extreme write pressure. They specifically want to see how you handle real-time data ingestion, manage global distribution for live events, and ensure data consistency without blocking the video stream experience.
Design a Dedicated News Feed Ranking Algorithm
Interviewers at Meta ask this to evaluate your ability to balance competing business objectives like user engagement and content freshness within a massive-scale system. They specifically assess your understanding of how machine learning models integrate with heuristic scoring, your approach to handling cold-start problems for new posts, and your strategic thinking regarding A/B testing frameworks to validate ranking improvements before global rollout.
Explain Consistent Hashing
Stripe interviewers ask this to evaluate your ability to design scalable, fault-tolerant distributed systems. They specifically want to see if you understand how to minimize data migration during cluster scaling while maintaining high availability and low latency for payment processing workloads.
Design an API for Financial Portfolio Tracking
Interviewers at Stripe ask this to evaluate your ability to design systems that balance real-time accuracy with eventual consistency, a core challenge in fintech. They specifically test how you handle external data staleness from volatile markets while ensuring the user interface remains responsive. The question assesses your judgment in choosing between strong consistency and availability when integrating third-party financial APIs.
Design a Push Notification Delivery System
Interviewers at Uber ask this to evaluate your ability to design high-throughput, reliable distributed systems that handle external dependencies like APNS and FCM. They specifically want to see how you manage token lifecycle, prevent notification spam through throttling, and ensure delivery guarantees in a multi-tenant environment where reliability directly impacts user engagement.
Design a Logging and Metrics Service
Interviewers at Netflix ask this to evaluate your ability to design scalable, high-throughput data pipelines under extreme load. They specifically assess your understanding of decoupling components using message brokers like Kafka, handling log ingestion bottlenecks, and balancing consistency versus availability in distributed systems.
Design a Serverless Data Processing System (AWS Lambda/Azure Functions)
Interviewers ask this to evaluate your ability to architect scalable, event-driven systems using specific cloud primitives. They assess if you understand the trade-offs between serverless components like AWS Lambda or Azure Functions versus traditional servers, specifically focusing on cost efficiency, cold start mitigation strategies, and designing robust data pipelines without managing infrastructure.
Design a Global Authentication Token Service
Interviewers at Airbnb ask this to evaluate your ability to design secure, low-latency systems for a global travel platform where trust is paramount. They specifically assess your understanding of distributed consistency, key management strategies across regions, and how to balance security with the need for rapid user authentication during high-traffic booking scenarios.
Design an Inventory Reservation System
Interviewers at Amazon ask this to evaluate your ability to design distributed systems that handle high concurrency and data consistency. They specifically want to see how you manage race conditions when multiple users attempt to reserve the same limited inventory simultaneously, and how you implement time-based expiration without blocking the checkout flow.
Design a System for E-commerce Search Filtering
Interviewers ask this to evaluate your ability to architect scalable systems handling high-concurrency read traffic, a core requirement for Amazon's massive marketplace. They specifically assess your understanding of inverted indexes, sharding strategies, and how to balance consistency with low-latency response times under heavy load.
Design a Simple Auction System
Interviewers at Stripe ask this to evaluate your ability to handle high-concurrency financial transactions where data consistency is non-negotiable. They specifically test your understanding of race conditions, the trade-offs between strong and eventual consistency, and how to implement real-time bid propagation without locking the entire system down.
Design a System for Monitoring E-commerce Price Changes
Interviewers at Amazon ask this to evaluate your ability to balance technical scalability with ethical constraints like politeness. They specifically test if you can design a distributed scraping system that handles high concurrency, detects price deltas efficiently without redundant storage, and respects rate limits to avoid IP bans while maintaining data integrity for competitive analysis.
Design a System for A/B Testing
Interviewers at Google ask this to evaluate your ability to design distributed systems with strict consistency and low-latency requirements. They specifically assess how you handle user bucketing logic, ensure feature flags remain consistent across sessions, and manage the trade-offs between availability and correctness in a high-scale environment.
Design a Distributed IDempotency Service
Interviewers at companies like Stripe ask this to evaluate your ability to handle critical financial constraints in distributed systems. They specifically test if you understand the trade-offs between strong consistency and availability, your knowledge of idempotency keys, and your capacity to design robust solutions that prevent double-spending or duplicate transactions under network failures.
Discuss Database Sharding Strategies
Meta interviewers ask this to assess your ability to design systems that scale beyond single-node limits. They specifically evaluate your understanding of distributed data trade-offs, your grasp of consistency models under partitioning, and whether you can anticipate operational complexities like rebalancing and cross-shard transactions in a high-traffic environment.
Design an Online Code Editor/Compiler Service
Interviewers at IBM ask this to evaluate your ability to balance functionality with critical security constraints. They specifically assess your understanding of sandboxing, resource isolation, and how to prevent malicious code from compromising host infrastructure while maintaining high availability for a distributed compilation service.
Design a System to Handle Schema Migration
Interviewers ask this to evaluate your ability to balance data integrity with service availability in high-scale environments like LinkedIn's feed. They assess whether you understand the risks of locking tables during traffic spikes and if you can architect a strategy that allows zero-downtime updates while maintaining backward compatibility between old and new application versions.
Design a CI/CD Pipeline
Interviewers ask this to evaluate your ability to architect scalable, resilient systems for modern microservices. They specifically test your understanding of the full software delivery lifecycle, from code commit to production rollout. At Microsoft, they value candidates who prioritize reliability, automated testing coverage, and zero-downtime deployment strategies like blue/green or canary releases.
Design a Public High-Scores Leaderboard
Interviewers ask this to evaluate your ability to design scalable, real-time systems under high concurrency. They specifically test your knowledge of data structures like Redis Sorted Sets for O(log N) operations and your awareness of security risks in gaming ecosystems, such as score manipulation or bot attacks.
Design a Multi-Tenant Application Architecture
Interviewers at Salesforce ask this to evaluate your ability to balance scalability with strict data security in a SaaS environment. They need to see if you understand the critical trade-offs between isolation and cost, specifically how to prevent one tenant from accessing another's data while maintaining a single codebase. This tests your architectural judgment regarding multi-tenancy patterns.
Design a Web Crawler
Interviewers ask this to evaluate your ability to architect distributed systems that balance scale, efficiency, and ethics. They specifically test your understanding of concurrency limits, resource management, and how to handle real-world constraints like politeness policies and duplicate detection in a high-throughput environment.
Design a System for Monitoring API Security
Stripe evaluates this question to assess your ability to architect secure, high-throughput systems for financial transactions. They specifically look for your understanding of real-time threat detection, the integration of Web Application Firewalls with logging pipelines, and your capacity to balance security rigor with low latency requirements essential for payment processing.
Design an Online Bookstore/E-commerce Catalog
Interviewers ask this to evaluate your ability to balance data consistency with scalability in a high-traffic environment. They specifically test if you can justify choosing SQL for transactional integrity versus NoSQL for flexible product attributes, and how you would architect a schema that supports Amazon's massive catalog diversity without sacrificing query performance.
Design a System for Data Auditing
Interviewers at Salesforce ask this to evaluate your ability to design immutable, high-integrity systems for compliance. They specifically test if you understand tamper-proofing mechanisms like hashing chains and how to balance strict audit requirements with system performance. The question reveals whether you can prioritize data security and regulatory adherence over convenience in a multi-tenant environment.
Design a Telemetry and Crash Reporting System
Interviewers at Apple ask this to evaluate your ability to balance high-volume data ingestion with strict privacy and integrity constraints. They specifically test your understanding of sampling strategies, error handling in distributed systems, and how to design for low-latency reporting without impacting the end-user experience on resource-constrained devices.
Design a Cloud Migration Strategy
Interviewers at Microsoft ask this to evaluate your ability to balance business continuity with technical modernization. They specifically assess whether you can articulate trade-offs between speed and long-term value, demonstrating strategic thinking about cost, risk, and the operational maturity required for cloud-native architectures.
Discuss CQRS (Command Query Responsibility Segregation)
Interviewers at Microsoft ask this to evaluate your ability to make trade-offs in system architecture. They want to see if you understand that optimizing for read performance often requires sacrificing immediate consistency. This question tests your depth in distributed systems, specifically how you handle data synchronization and eventual consistency patterns in large-scale environments.
Design a System for Monitoring System Metrics (Prometheus)
Interviewers at Netflix ask this to evaluate your ability to design scalable, distributed monitoring systems that handle high-velocity data. They specifically want to see if you understand the trade-offs between pull and push models in a microservices environment, where network reliability and system resilience are critical for maintaining service level objectives during outages.
Design a Load Balancer
Interviewers at Microsoft ask this to evaluate your ability to architect distributed systems that balance scalability with reliability. They specifically test if you understand the trade-offs between Layer 4 and Layer 7 routing, how to handle node failures gracefully through health checks, and whether you can design for high availability without creating single points of failure in a large-scale cloud environment.
Design a Cloud Cost Monitoring and Alerting System
Interviewers at Spotify ask this to evaluate your ability to balance cost efficiency with engineering velocity. They want to see if you can design a system that provides real-time visibility across distributed teams without becoming a bottleneck. This tests your understanding of cloud billing APIs, data aggregation strategies, and your capacity to build scalable alerting mechanisms that prevent budget overruns while maintaining developer autonomy.
Design an Employee Directory Service (LDAP/Active Directory)
Interviewers at Salesforce ask this to evaluate your ability to design scalable, secure identity systems. They specifically test your understanding of hierarchical data modeling, real-time synchronization challenges in distributed environments, and how you prioritize security principles like least privilege while maintaining high availability for enterprise clients.
Design a Server-Side Analytics Dashboard
Salesforce asks this to evaluate your ability to architect scalable data pipelines that handle high-volume event ingestion. They specifically want to see if you understand the trade-offs between transactional databases and OLAP systems like Cube or ClickHouse for complex aggregations. The question tests your capacity to design a backend that balances low-latency querying with cost-effective storage for internal analytics tools.
Design a System for Tracking Daily Active Users (DAU)
Interviewers at Meta ask this to evaluate your ability to balance accuracy with massive scale. They specifically want to see if you understand the trade-offs between exact counting and probabilistic algorithms like HyperLogLog when handling billions of events daily. It tests your grasp of distributed systems, data consistency, and resource optimization under strict latency constraints.
Design a Serverless Real-time Data Pipeline
Interviewers at Apple ask this to evaluate your ability to architect scalable, cost-efficient systems using modern cloud primitives. They specifically test your understanding of event-driven architectures, data consistency trade-offs, and how to leverage managed services like Kinesis and Lambda to eliminate operational overhead while handling unpredictable real-time traffic spikes.
Design a Customer Onboarding Pipeline
Interviewers ask this to evaluate your ability to design resilient, event-driven systems that handle complex business logic. Specifically, they want to see if you can model state transitions correctly, ensure data consistency across distributed tasks, and gracefully manage failures when integrating with external CRM or payment services typical of enterprise platforms like Salesforce.
Design a Global Rate Limiter
Interviewers at Stripe ask this to evaluate your ability to design resilient distributed systems under strict consistency constraints. They specifically test your understanding of global state management, latency trade-offs in centralized stores like Redis, and your capacity to select appropriate algorithms like Token Bucket for fair throttling across geographically dispersed servers.
Design an Image Processing and Filtering Pipeline
Meta interviewers ask this to evaluate your ability to design scalable, fault-tolerant systems that handle high-throughput media workloads. They specifically test your understanding of asynchronous processing patterns, resource management via worker pools, and data durability through job queue persistence. The question reveals whether you can balance latency requirements with system resilience when processing user-generated content at scale.
Design an Automated Customer Support Triage System
Interviewers at Adobe ask this to evaluate your ability to balance scalable architecture with user-centric AI logic. They specifically want to see if you can handle ambiguous requirements, design a system that integrates NLP for ticket classification, and prioritize low latency while maintaining high accuracy in routing sensitive customer data across distributed services.
Design a System for Distributed Tracing (Jaeger/Zipkin)
Interviewers ask this to evaluate your ability to design scalable, high-performance systems that handle massive data ingestion without blocking user requests. At Google, they specifically test if you understand the trade-offs between consistency and availability in distributed environments, and whether you can implement efficient sampling strategies to manage storage costs while retaining critical debugging data.
Design a Distributed Queue (Kafka/SQS)
Interviewers at Amazon ask this to evaluate your ability to design scalable, fault-tolerant systems that handle high-throughput data streams. They specifically assess your understanding of trade-offs between consistency and availability, your grasp of partitioning strategies for parallelism, and your knowledge of delivery semantics like at-least-once versus exactly-once in real-world distributed environments.
Design a Disaster Recovery Plan
Amazon asks this to evaluate your ability to design resilient systems under pressure, a core component of their Leadership Principle of Customer Obsession. They need to see if you can balance cost against availability while defining clear metrics like RPO and RTO. The question tests your capacity to automate failure recovery rather than relying on manual intervention.
Design a Distributed Counter Service
Interviewers at Google ask this to evaluate your ability to balance trade-offs between consistency, availability, and partition tolerance in high-scale environments. They specifically want to see if you can design a system that handles millions of concurrent writes without locking bottlenecks, while making informed decisions about eventual versus strong consistency based on business requirements.
Design a Geolocation Service (IP to Location)
Interviewers ask this to evaluate your ability to balance data accuracy with latency in a read-heavy system. They specifically test your understanding of trade-offs between IP geolocation databases, caching hierarchies, and handling edge cases like dynamic IPs or mobile roaming.
Design a CAPTCHA Service
Interviewers at Microsoft ask this to evaluate your ability to design secure, scalable systems that balance user experience with robust bot mitigation. They specifically look for your understanding of the adversarial nature of CAPTCHA, where attackers constantly evolve to bypass simple challenges while legitimate users require frictionless access.
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