[Solved] Which scenario best shows when to use an idempotency key in a REST API? — Ans: When a client retries a payment request after a network failure | Rest API

Rest API - Advanced Patterns

Which scenario best shows when to use an idempotency key in a REST API?

AWhen a client requests a list of products

BWhen a client retries a payment request after a network failure

CWhen a client logs in with username and password

DWhen a client fetches static images

Step-by-Step Solution

Solution:

Step 1: Identify operations that need safe retries
Operations like payments that change server state need idempotency keys to avoid duplicates on retry.
Step 2: Match scenarios with this need
Retrying a payment request fits this need, unlike fetching data or logging in.
Final Answer:
When a client retries a payment request after a network failure -> Option B
Quick Check:
Use case for idempotency key = state-changing retries [OK]

Quick Trick: Use idempotency keys for retrying state-changing requests [OK]

Common Mistakes:

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