Design an API Gateway
Explain the functions of an API Gateway (Authentication, Routing, Metering, Caching). Discuss implementing it using Nginx, Envoy, or a custom service.
Why Interviewers Ask This
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.
How to Answer This Question
1. Clarify requirements immediately by asking about expected traffic volume, security standards, and latency constraints specific to enterprise data handling. 2. Outline core responsibilities first: authentication, routing, caching, and metering, explaining why each is critical for API stability. 3. Propose a concrete architecture using a reverse proxy like Nginx or Envoy, detailing how they handle load balancing and SSL termination. 4. Discuss implementation strategies for custom logic, such as sidecar patterns or serverless functions for complex transformations. 5. Conclude with scalability considerations, mentioning horizontal scaling of gateway instances and monitoring metrics to ensure reliability under peak loads.
Key Points to Cover
- Centralizing cross-cutting concerns like auth and logging improves system modularity
- Explicitly mentioning specific tools like Envoy or Nginx demonstrates practical knowledge
- Explaining how caching reduces backend load shows performance optimization skills
- Connecting metering to business value (billing/tenancy) highlights strategic thinking
- Addressing scalability ensures the solution works for enterprise-level traffic
Sample Answer
An API Gateway acts as the single entry point for all client requests, essential for managing complexity in microservices. At Salesforce, where we handle massive volumes of customer data, the gateway must enforce strict…
Common Mistakes to Avoid
- Focusing only on code implementation without discussing architectural trade-offs
- Ignoring security implications like token validation or rate limiting
- Proposing a monolithic gateway instead of considering distributed deployment
- Forgetting to mention monitoring and observability as part of the design
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