Glossary
Idempotency
A guarantee that repeating the same request produces the same result rather than performing the action twice.
Networks fail after the server has acted but before the client sees the response. Without idempotency, the client's retry creates a second transaction. With it, the client sends a unique idempotency key, and the server returns the original result for any repeat of that key.
In money movement this is not an optimization — it is the difference between a resilient system and one that occasionally double-charges customers under load.
What it covers in practice
- Required on all mutating financial endpoints
- Keys are client-generated and unique per logical operation
- Retries return the original outcome, not a new one