AWS doesn’t keep instances warm based on forecasted demand. It uses one instance per request and instances stay warm once they are started for a predetermined amount of time based on the size of tyrvlambda environment.

It depends on the stack. You have to be more mindful of cold start when running Java/Clojure apps, less with JS and .net. There are some good benchmarks out there. There are also some easy ways to keep routes warm, although for certain setups I imagine that could be quite expansive, though still probably not expensive.

I don't know if anything has changed since, but we definitely hot cold start perf issues on lesser used routes at a company I was with 18 months ago.