What Causes a 409 Status Code and How Do You Resolve It? or Getting a 409 Status Code – What’s the Co

The 409 status code is such a pain. In my case, it was a race condition—two requests trying to update the same resource.

Fix? Implement optimistic locking or use a mutex if you’re on the backend.

Also, check out the RFC for HTTP 409—it’s dry but weirdly helpful.