Duplicate order submission is a classic idempotency problem that can arise from user double-clicks, network retries, or message queue redelivery. A robust solution requires a layered approach rather than a single mechanism. The first layer is frontend control, such as disabling buttons after the first click, which reduces accidental duplicates but is not foolproof. The second layer uses a distributed token, typically generated by the server and stored in Redis, that must be presented with each order request and consumed atomically. The third layer enforces a unique constraint on the database, such as a business order number, to reject duplicates at the persistence level. Finally, a scheduled reconciliation job can detect and resolve inconsistencies that slip through the other layers. For high-concurrency scenarios, Redis atomic operations and Lua scripts are essential to ensure that token consumption and order creation are race-condition-free. While the article provides a Java AOP implementation, the underlying principles are language-agnostic and applicable to any distributed system.
A practical guide to preventing duplicate order submissions using a four-layer defense strategy, from frontend controls to database constraints and reconciliation.