retry contract

Idempotency

Also known as · idempotent · duplicate request safety · retry safety

Definition

The property that repeated processing of the same intent converges on the same observable business state as one processing. It limits duplicate effects instead of pretending retries do not happen.

Searchable examples

Idempotency-Key: order-123
ON CONFLICT DO NOTHING

Short example

INSERT INTO jobs (request_key, state)
VALUES ($1, 'accepted')
ON CONFLICT (request_key) DO NOTHING;

Define the key scope, retention window, and conflict response too.

Compare with

API contractAPI Contractboundary agreementAn agreement that makes a provider and its consumers interpret inputs, outputs, authorization, errors, and state in the same way. It owns the observable boundary rather than a screen or implementation shape.

Terms that compare with this term

Single Source of Truthdesign principleA principle that gives one authoritative source the meaning and write authority for a fact while treating other representations as derived state. It clarifies ownership and synchronization boundaries; it does not mean copies never exist.
Database migrationDatabase Migrationschema changeA versioned change that moves operational data structures or constraints from one state to the next. Successful SQL syntax is a separate judgment from compatibility and recoverability.

Related notes

REST API introduction
Idempotent migrations and partial-failure recovery

Related courses

Step 2 — Fix HTTP retries and request correlation