[z1mm32m4n]

Ironically, one of the easier ways TypeScript has been able to work quickly is by skipping the type inference Flow does. It’s a trade off. The Flow team was advised that this approach would have performance problems early on in the project, and opted to focus on type system features first and perf second.

[shados]

Flow's perf issues has more to do with bugs than anything. Its usually pretty near instant even on big projects, but do one little thing wrong somewhere that hits an edge case and everything goes to hell and you'll never find where it came from.