What is a transaction and explain ACID properties?

SQL
Medium
Flipkart
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Defines a transaction and details Atomicity, Consistency, Isolation, and Durability guarantees.

Why Interviewers Ask This

Transactions ensure reliable data processing. Interviewers want to confirm you understand how to maintain data integrity during failures or concurrent access.

How to Answer This Question

Define a transaction as a sequence of operations treated as a single unit. Explain ACID: Atomicity (all or nothing), Consistency (valid state), Isolation (no interference), Durability (permanent). Use banking transfer as an example.

Key Points to Cover

  • Transaction definition
  • ACID breakdown
  • Reliability assurance
  • Failure handling

Sample Answer

A transaction is a logical unit of work where all steps succeed or none do. ACID properties ensure reliability: Atomicity guarantees completeness, Consistency maintains valid states, Isolation prevents interference between concurrent transactions, and Durability ensures changes persist even after a crash. This is vital for financial applications.

Common Mistakes to Avoid

  • Misinterpreting Isolation levels
  • Confusing Durability with Backup
  • Ignoring concurrency issues

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