LESSON 06 / 22·2 min readFoundation

PUT vs PATCH, and what does idempotent mean?

Try code in the playground

01 Understand02 Recall 03 Prepare

Understand the concept

PUT is defined around creating or replacing the state of a target resource, while PATCH applies a described partial change. Idempotency means repeating an identical operation has the same intended server-side effect as doing it once. It does not require every repeated response to contain the same status or body.

Important ideas

PUT replaces the target representation; PATCH applies a partial change.
Idempotent means repeating the same request has the same intended effect.
PUT and DELETE are idempotent by semantics; PATCH depends on the operation.
“Set quantity to 3” can be idempotent; “increase quantity by 3” generally is not without a deduplication mechanism.

Work through the example

PUT /profiles/42 with the same profile representation leaves the same intended state after repetition.
PATCH /counters/42 with “increment by 1” changes the state again on each attempt unless an idempotency key is enforced.
A repeated request can have a different response while still being idempotent.

PAUSE & RECALL

Can you explain it without the notes?

PUT vs PATCH, and what does idempotent mean?

Use your own words. Explain an example and one limitation before checking the explanation.

Check your explanation

PUT is defined around creating or replacing the state of a target resource, while PATCH applies a described partial change. Idempotency means repeating an identical operation has the same intended server-side effect as doing it once. It does not require every repeated response to contain the same status or body.

CONNECT IT TO YOUR INTERVIEW

Turn this concept into a clear answer.

A repeated DELETE can return 404 after an initial success while remaining idempotent because the resource stays deleted.

PUT vs PATCH, and what does idempotent mean?

Node.js·HTTP & APIs

PUT is defined around creating or replacing the state of a target resource, while PATCH applies a described partial change. Idempotency means repeating an identical operation has the same intended server-side effect as doing it once. It does not require every repeated response to contain the same status or body.

Foundation2 min read

Practice this concept

YOUR NEXT STEP

Keep connecting the ideas.

Next lesson: HTTP/1.1 vs HTTP/2 vs HTTP/3?

Adapted from 02_NODE_EXPRESS_HTTP.md · “PUT vs PATCH, and what does idempotent mean?”. Examples are study fragments; framework behavior can depend on your version.