Idempotency of methods in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does idempotency mean in the context of REST API methods?

Idempotency means that making the same API request multiple times results in the same effect as making it once. The server state does not change after the first request.

beginner

Which HTTP methods are idempotent by definition?

GET, PUT, DELETE, HEAD, OPTIONS, and TRACE are idempotent methods. POST is not idempotent by default.

beginner

Why is the POST method generally not idempotent?

POST usually creates new resources or triggers operations that change server state each time it is called, so repeating it can cause multiple changes.

intermediate

How can you make a POST request behave in an idempotent way?

By using unique client-generated IDs or tokens with the POST request, the server can recognize repeated requests and avoid creating duplicates.

beginner

What is a real-life example of idempotency in REST APIs?

If you send a DELETE request to remove a user account, sending it multiple times will have the same effect as sending it once: the account is deleted and further requests do nothing.

Which HTTP method is NOT idempotent by default?

A POST

B GET

C PUT

D DELETE

POST is not idempotent because it usually creates new resources or triggers changes each time it is called.

What does it mean if an API method is idempotent?

A Multiple identical requests have the same effect as one

B It returns different data on each call

C It changes server state every time it is called

D It only works once and then fails

Idempotent methods produce the same result no matter how many times the same request is made.

Which HTTP method is typically used to update a resource and is idempotent?

A CONNECT

B POST

C PATCH

D PUT

PUT replaces or updates a resource and is idempotent because repeating it does not change the result.

How can you ensure a POST request is idempotent?

A By sending it multiple times quickly

B By including a unique client-generated ID

C By using GET instead

D By ignoring server responses

Using a unique ID lets the server detect repeated requests and avoid duplicate actions.

Which of these HTTP methods is idempotent?

A POST

B PATCH

C DELETE

D CONNECT

DELETE is idempotent because deleting the same resource multiple times has the same effect as deleting it once.

Explain idempotency in REST API methods and why it matters.

Think about what happens if you send the same request many times.

Describe how you can design a POST method to behave idempotently.

Consider how the server can recognize repeated requests.