Back to All Blogs1 min read5 Sept 2026
Backend Engineering Essentials · Part 4 of 7
Idempotency: Making Retries Safe in Distributed Systems
“Learn why retries create duplicates and how idempotency keys solve the problem.”
Idempotency
Distributed systems experience ambiguous failures.
Client sends payment request
↓
Server processes payment
↓
Network disconnects
↓
Client never receives responseIdempotency Key
POST /payments
Idempotency-Key: checkout_8f3daGenerating diagram...
Database Enforcement
CREATE UNIQUE INDEX payments_idempotency_key
ON payments(idempotency_key);Note
Retries are normal. Design important operations so retries are safe.
Useful for payments, orders, booking, webhooks, job processing and email workflows.
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