You are building a REST API for processing orders where clients may retry requests. Which design best uses idempotency keys to avoid charging customers multiple times?

hard📝 Application Q8 of 15

Rest API - Advanced Patterns

AGenerate a new payment transaction for every request regardless of the idempotency key

BStore the payment result keyed by the idempotency key and return it on retries without reprocessing

CIgnore idempotency keys and rely on client-side retry logic only

DDelete stored idempotency keys immediately after processing to save memory

Step-by-Step Solution

Solution:

Step 1: Understand retry risks
Retries can cause duplicate charges if requests are processed multiple times.
Step 2: Use idempotency keys
By storing the payment result with the key, the server can return the same result on retries.
Step 3: Avoid duplicate processing
This prevents multiple charges for the same order.
Final Answer:
Store the payment result keyed by the idempotency key and return it on retries without reprocessing -> Option B
Quick Check:
Persist results by key to prevent duplicate payments [OK]

Quick Trick: Persist results by key to avoid duplicates [OK]

Common Mistakes:

MISTAKES

Processing every request as new
Relying only on client retries
Deleting keys too soon causing duplicates

Master "Advanced Patterns" in Rest API

9 interactive learning modes - each teaches the same concept differently

Learn Why Deep Visual Try Challenge Project Recall Time

Want More Practice?

15+ quiz questions · All difficulty levels · Free

Free Signup - Practice All Questions

More Rest API Quizzes

You are building a REST API for processing orders where clients may retry requests. Which design best uses idempotency keys to avoid charging customers multiple times?

Step 1: Understand retry risks

Step 2: Use idempotency keys

Step 3: Avoid duplicate processing

Final Answer:

Quick Check:

Want More Practice?