Backend & systems·Concurrency and coordination
you run it twice with the same input and get byte-identical output, because nothing inside it reads the clock or a random number.
Deterministic
The property that the same inputs always produce the same output. It is about reproducibility, not about repeat-safety: a deterministic function can still be unsafe to run twice if it has side effects, and an idempotent operation can be non-deterministic in what it returns. Determinism is what makes replay, caching and testing possible.