What is idempotency in API calls, and why is it important in microservices?

Short answer: Idempotency ensures that making the same API call multiple times has the same effect, i.e., it does not cause unintended side effects or inconsistencies.

Explain a bit more

It is crucial in microservices because: Fault Tolerance: In a distributed system, a service may receive the same request multiple times due to retries or network issues. Idempotency ensures that these repeated requests do not result in duplication or errors. Consistency: It ensures that the system remains in a consistent state, even if a request is accidentally repeated. Example: A Payment Service processing the same payment request multiple times due to a network retry would not result in multiple charges because the API is designed to ignore duplicate requests with the same unique transaction ID. API Design & Security

Real-world example (ShopNest)

ShopNest splits Catalog, Cart, Order, and Payment into services so teams can deploy catalog changes without redeploying payments.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.