Idempotency keys for safe retries in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an idempotency key in REST APIs?

An idempotency key is a unique identifier sent with a request to ensure that even if the request is repeated, the server processes it only once, preventing duplicate actions.

beginner

Why are idempotency keys important for safe retries?

They help avoid duplicate operations when a client retries a request due to network issues or timeouts, ensuring the server does not perform the same action multiple times.

intermediate

How should a client generate an idempotency key?

Clients should generate a unique, random string (like a UUID) for each operation that needs safe retry, and send it with the request header.

intermediate

What should the server do when it receives a request with a previously seen idempotency key?

The server should return the same response as the original request without performing the operation again, ensuring the request is idempotent.

beginner

Give a real-life example where idempotency keys prevent problems.

When submitting a payment, if the client retries due to a timeout, the idempotency key ensures the payment is only processed once, avoiding double charges.

What does an idempotency key help prevent in REST API requests?

A Changing the request method

B Duplicate processing of the same request

C Faster response times

D Encrypting the request data

Idempotency keys prevent duplicate processing by identifying repeated requests.

Where is an idempotency key usually sent in a REST API request?

A In the server response

B Only in the URL path

C In the request header

D In the database

Clients send idempotency keys in the request header to identify the request uniquely.

If a server receives a request with a known idempotency key, what should it do?

A Return the original response without reprocessing

B Process the request again

C Ignore the request

D Delete the idempotency key

The server returns the original response to avoid duplicate operations.

Which of these is a good way to generate an idempotency key?

A Use a random UUID string

B Use the current timestamp only

C Use the client's IP address

D Use the HTTP method name

A random UUID ensures uniqueness for each request.

Idempotency keys are most useful when:

A Requests are read-only

B Requests are always successful

C The server never fails

D Requests might be retried due to network issues

Retries due to network problems can cause duplicate requests, which idempotency keys help prevent.

Explain what an idempotency key is and how it helps in safe retries in REST APIs.

Think about how to avoid doing the same action twice when a request is repeated.

Describe the server's behavior when it receives a request with an idempotency key it has seen before.

Consider how the server avoids repeating work for the same request.