Idempotency Key
In plain terms
A unique token ensuring a request runs only once.
Going deeper
An idempotency key lets a client safely retry a request; the server uses the key to avoid performing the operation twice. It deduplicates retries.
Under the hood
Critical for payments and POST operations; the server caches results per key to return the same outcome.
Examples
Payment APIs (Stripe), safe retries, preventing double charges, POST safety.
Think of it like...
Like a claim ticket ensuring you're served once even if you hand it over twice.