How to Prevent Duplicate API Processing with Idempotency in MuleSoft

<p>In distributed systems, failure is not an exception—it’s the default.</p> <p>Network calls fail. Services timeout. APIs return 500s. The real question isn’t <em>“Will things

<p>Two things quietly decide whether a small application survives being used: whether its reads<br /> are indexed, and whether its writes can be repeated safely. They are usually

<p>A pipeline that runs twice should produce the same result as one that runs once. That property is idempotency, and its absence is one of the most common sources of silent data

<p><em>Originally published on <a href="https://loopandretry.github.io/posts/what-idempotent-means/?ref=devto" rel="noopener noreferrer">Loop &amp; Retry</a> — field notes on

<h1> Idempotency Keys: The API Pattern That Saves You From Duplicate Payments and Phantom Records </h1> <p>Your user clicks "Pay" and nothing happens. So they click again. Your

<p>You hit "Submit Order" and nothing happens. The spinner just spins. Is it processing? Did the request get lost? You click again.</p> <p>If the API on the other end does not

<h1> API layer pattern (HTTP) </h1> <h2> 1) Contract </h2> <ul> <li>Require <code>Idempotency-Key</code> on <strong>POST</strong> that creates resources (optional on GET, safe

<p>A user clicks “Pay”, the network drops, the client retries… and your backend creates <strong>two</strong> payments.</p> <p>This isn’t a “frontend bug”. Retries happen