Idempotency Patterns

Patterns for designing APIs and systems that handle retries safely without duplicate side effects.

When to Use This Skill

• Designing APIs that handle retries safely
• Implementing idempotency keys
• Preventing duplicate operations
• Building reliable payment/order systems
• Handling network failures gracefully

What is Idempotency?

Idempotent operation: Same result regardless of how many times executed

f(x) = f(f(x)) = f(f(f(x))) = ...