How does this skill help with payment processing?

It provides patterns to ensure that if a network failure occurs after a payment is authorized but before the client receives a response, a retry will return the existing authorization rather than creating a second charge.

Does this skill cover database-level deduplication?

Yes, it includes strategies for using unique database constraints and 'ON CONFLICT' clauses to ensure data integrity at the persistence layer even when application logic retries.

Which HTTP methods are idempotent by default?

GET, HEAD, OPTIONS, PUT, and DELETE are considered idempotent according to HTTP specifications, meaning multiple identical requests should have the same effect as a single request.

What is an idempotency key?

An idempotency key is a unique value generated by the client and sent with a request. The server uses this key to recognize subsequent retries of the same operation, ensuring it only processes the logic once while returning the same response.

Idempotency Design Patterns

Name: Idempotency Design Patterns
Author: melodic-software

bymelodic-software

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API Development

Provides expert architectural patterns for designing idempotent APIs and systems that handle retries safely without duplicate side effects.

About

This skill equips Claude with comprehensive strategies for building resilient distributed systems where operations must be executed safely across unreliable networks. It covers the implementation of idempotency keys, request fingerprinting, and database-level deduplication, ensuring that retries don't lead to double charges, duplicate orders, or data corruption. Whether you are architecting payment gateways, message queues, or RESTful APIs, this skill provides the implementation patterns needed to achieve reliable at-most-once and exactly-once processing semantics.

Key Features

Deduplication strategies using Redis stores, database constraints, and optimistic locking
Architectural guidance on handling in-flight requests and concurrent race conditions
Implementation of Idempotency Key patterns and request fingerprinting techniques
Domain-specific patterns for payments, order management, and event-sourced systems
12 GitHub stars
Safe retry logic for non-idempotent HTTP methods like POST and PATCH

Use Cases

Building payment processing systems that prevent double-charging customers during network timeouts
Refactoring legacy REST APIs to support robust client-side retry mechanisms
Designing microservices that require exactly-once message processing and delivery

About

Key Features

Deduplication strategies using Redis stores, database constraints, and optimistic locking
Architectural guidance on handling in-flight requests and concurrent race conditions
Implementation of Idempotency Key patterns and request fingerprinting techniques
Domain-specific patterns for payments, order management, and event-sourced systems
12 GitHub stars
Safe retry logic for non-idempotent HTTP methods like POST and PATCH

Use Cases

Building payment processing systems that prevent double-charging customers during network timeouts
Refactoring legacy REST APIs to support robust client-side retry mechanisms
Designing microservices that require exactly-once message processing and delivery