AI engineering glossary · Web APIs HTTP
What is idempotency key?
Idempotency key: A unique value, usually a random string sent in a header, that a client attaches to a request so the server can recognise a retry of the same operation and return the original result instead of running it twice. Payment APIs rely on it to avoid double charges.
Idempotency key: an example
A client sends Idempotency-Key: 7f3a... with a payment call; after a timeout it resends the same key and is charged only once.
Related terms
More Web APIs HTTP terms
Where you learn it
Idempotency key is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.