If your API double-bills on a retry, goes belly-up under load or you’re afraid to scale it, I can help. I build backends that last.

I add idempotency so you only process a repeated request once (no more double charges or duplicate records), I add rate limiting so one user can't take you down, and I fix the concurrency bugs that corrupt your data silently under load. These are the same patterns that payment systems build on.

I maintain an open source library for this (idempotency-kit) so you can see how I do it.