http://foojayio.github.io/website/today/author/youssef/Articles written by Youssef Ben Henda on foojay.io - Friends Of OpenJDKHugoen-usTue, 04 Aug 2026 22:11:22 +0000http://foojayio.github.io/website/today/idempotent-spring-boot-starter/Tue, 04 Aug 2026 22:11:22 +0000http://foojayio.github.io/website/today/idempotent-spring-boot-starter/<h2 id="idempotent-rest-endpoints-without-the-boilerplate">Idempotent REST Endpoints Without the Boilerplate</h2> <h2 id="stop-charging-your-users-twice-idempotent-rest-endpoints-with-one-annotation">Stop Charging Your Users Twice: Idempotent REST Endpoints with One Annotation</h2> <h2 id="the-problem-nobody-talks-about-until-production">The problem nobody talks about until production</h2> <p>A user taps &ldquo;Pay.&rdquo; The request times out. Their app retries. Your server charges them twice.</p> <p>You didn&rsquo;t write a bug. The network did. But your users don&rsquo;t care about that distinction.</p> <p>The idempotency problem shows up in more places than payments. A load balancer replays a timed-out request. A mobile client double-taps a submit button. A Kubernetes pod retries after a restart. From the server&rsquo;s perspective, all of these look identical: a second POST that arrives after the first one already executed.</p>