Idempotency

Idempotency is an important concept that plays a role in software development and web services. It helps make systems more robust and predictable by ensuring that repeated requests have the same effect, regardless of how many times they are executed. This is particularly relevant for error handling and system recovery.

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Content type

Concept

Theoretical construct: explains a term, principle, or mental model.

Classification level

Foundation

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In brief

Idempotency in brief

Idempotency describes an operation whose repeated execution has the same effect as executing it once.

Where does it come from?

The term comes from mathematics and was adopted for fault-tolerant software and HTTP interactions; RFC 9110 explicitly relates it to the semantics of methods such as PUT and DELETE.

The mental model

A request may arrive again after a timeout. The operation therefore checks keys, state, and intended effect so that a second call creates no additional side effect.

Key building blocks

Core idea

Idempotency is a fundamental concept in computer science that describes a function or operation that yields the same result when executed multiple times.

Mechanism

It helps make systems more robust and predictable by ensuring that repeated requests have the same effect, regardless of how many times they are executed.

Practice context

This is particularly relevant for error handling and system recovery.

When is it useful?

Idempotency is especially valuable for retries, webhooks, and distributed writes. It requires an appropriate state and key strategy; it guarantees neither exactly-once processing nor conflict-free business decisions.

RFC 9110 HTTP Semantics

Why is this building block relevant?

Idempotency is a fundamental concept in computer science that describes a function or operation that yields the same result when executed multiple times.