quayside is my idempotency library for Node. js. The whole API fits in one sentence: execute(key, fn) runs a function exactly once per key — if it already ran, you get the stored result back; if it is running right now, you don't run it again.
Source: [Dev.to](https://dev.to/pinceladasdaweb/my-idempotency-library-had-one-job-a-dropped-connection-made-it-run-the-payment-twice-nnh)