What is an idempotency key?

An idempotency key is a unique value sent by the client that allows the server to identify subsequent retries of the same request, ensuring the operation is only performed once.

When should I implement idempotency?

Idempotency is critical for any API mutation that involves financial transactions, order placement, or external side effects where duplicate execution would cause data or financial errors.

Does this skill support different database types?

Yes, it provides implementation patterns for Redis-based caching as well as relational database (SQL) schemas with conflict resolution logic.

How are expired idempotency keys handled?

The skill includes multiple TTL (Time-To-Live) strategy examples, including scheduled SQL cleanup jobs and application-level cron tasks to prevent table bloat.

Can this be used with Node.js and Python?

Absolutely. The skill features implementation patterns in JavaScript/Node.js, Python, and SQL, making it compatible with most modern backend architectures.

API Idempotency Handling

Name: API Idempotency Handling
Author: secondsky

bysecondsky

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API Development

Implements production-ready idempotent API operations using Redis, database constraints, and safe retry patterns to prevent duplicate processing.

This skill provides comprehensive patterns and implementations for ensuring API operations produce identical results regardless of how many times they are executed. It includes ready-to-use middleware for Redis caching, robust database schemas for SQL-backed idempotency, and specialized logic for handling payments and webhooks. By implementing these patterns, developers can eliminate race conditions, prevent duplicate charges, and handle network retries safely in distributed systems and high-stakes environments.

Key Features

0121 GitHub stars

02Database-backed transaction patterns using SQL constraints and request hashing

03Atomic operation handling to prevent race conditions during concurrent requests

04Automated TTL (Time To Live) cleanup strategies for Postgres, Node.js, and Python

05Redis-based idempotency middleware for high-performance request caching

06Standardized patterns for payment processing and webhook retry safety

Use Cases

01Ensuring webhook handlers can safely process retried events without side effects

02Preventing double-charging and duplicate transactions in payment processing systems

03Implementing safe retry logic for order creation and inventory management APIs

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add secondsky/claude-skills idempotency-handling

For use in Claude.ai and ChatGPT

Download Skill