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Java · Library & reference application
Java Idempotency Kit
Idempotent request processing for Java 21 and Spring Boot with atomic PostgreSQL leases, safe replay, and explicit failure boundaries.
The challenge
Retried requests must not execute payments or orders twice. Concurrency, crashes, and key conflicts still need explicit and reviewable behavior.
The result
A modular library with a Spring Boot starter, memory and JDBC stores, plus an executable order API as an architecture example.
What this project demonstrates
Reviewable decisions instead of slogans.
- Atomic lease takeover and compare-and-set transitions
- Safe result replay and key-conflict detection
- PostgreSQL, Flyway, Micrometer, and Testcontainers
- Documented guarantees and deliberately named crash windows
Technologies