#api

The property of an operation where performing it multiple times produces the same result as performing it once. Idempotent API endpoints are critical for safe retries — if a network error occurs, the client can re-send the request without fear of duplicating side effects like charges or database records.

“Pass an idempotency key with payment requests so retries don't charge the customer twice.”

A technique for controlling the frequency of requests a client can make to an API or service within a given time window. Rate limiting protects systems from abuse, prevents overload, and ensures fair resource allocation among consumers. Responses typically include headers indicating current usage and remaining quota.

“The API returned a 429 Too Many Requests error once rate limiting kicked in at 100 calls per minute.”

A user-defined HTTP callback that fires automatically when a specific event occurs in a source system. Rather than polling an API repeatedly, webhooks push data to a listener URL the moment something happens — making integrations real-time and efficient.

“We set up a webhook so Slack gets notified instantly every time a new definition is published.”