Idempotency
ELI5 — The Vibe Check
Idempotency means 'doing the same thing twice gives you the same result.' It's like pressing an elevator button multiple times — you still go to the same floor, not floor times 5. In APIs, it means if a network hiccup causes your payment request to be sent twice, the customer only gets charged once. It's the reason you don't get double-billed.
Real Talk
Idempotency is the property where making the same request multiple times produces the same result as making it once. In API design, it's implemented via idempotency keys — unique identifiers sent with requests to prevent duplicate operations. It's critical for payment processing, order creation, and any operation where duplicates cause real-world harm.
When You'll Hear This
"Every payment request includes an idempotency key so network retries don't cause double charges." / "PUT and DELETE are naturally idempotent; POST operations need idempotency keys."
Related Terms
Exactly-Once Delivery
Exactly-once delivery is the holy grail of messaging — every message delivered exactly one time, no more, no less.
REST (Representational State Transfer)
REST is a set of rules for how APIs should behave. Think of it as the etiquette guide for servers and clients talking to each other.
Retry Logic
Retry Logic automatically retries failed requests instead of giving up on the first failure. But done wrong, retries cause thundering herds.
Stripe API
Stripe API is the gold standard of payment APIs — it's so well-designed that other companies use it as a template for their own APIs. It handles credit car