Idempotency in 1 diagram and 144 words
Explained as simply as possible… but not simpler.
An operation is idempotent if performing it multiple times has the same effect as doing it once.
In distributed systems and APIs, failures or retries are common. Idempotency ensures that reprocessing a request (e.g., due to a timeout or client retry) doesn’t cause unintended side effects like duplicate charges or records.
Use idempotency when building APIs or services where clients might retry requests - especially for operations like payments, updates, or resource creation.
You need to know
Idempotency key helps track requests: Clients often send a unique key (like a UUID) with each request, so the server can detect and discard duplicates.
Not all HTTP methods are idempotent:
GET,PUT, andDELETEare typically idempotent;POSTis not unless explicitly handled that way.Applies to side effects, not just responses: It’s ensuring the system state doesn’t change undesirably, not just returning the same result.
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