The pricing on this takes a bit of mental processing. So take us-east-1; normally you pay $0.000016667 for every GB-second + $0.20 per 1M requests. By my read

The pricing on this takes a bit of mental processing. So take us-east-1; normally you pay $0.000016667 for every GB-second + $0.20 per 1M requests. By my reading if you turn on reserved concurrency 1 to keep a low-usage Lambda hot it changes to: $0.000004167 for every GB-second: so $10.80 for a 30-day month. Requests are $0.20 per 1M requests - same. Duration changes to $0.000009722 for every GB-second for the Lambda-that-is-kept hot. OK I have to put those on lines next to each other to see it, too many zeroes for my eyes: $0.000016667 on-demand vs: $0.000009722 reserved concurrency Alright, so that's 58% of the normal cost, so you can draw a graph and find some crossover point of duration where that gets cheaper - exercise left to the reader - but that fights against the Lambda already being kept hot by usage. I can't process intuitively whether this is a good deal or not. It's awkward - Lambdas spinning a microVM in 1-2s for cold starts (NodeJS, maybe dotnet, I don't use it but I understand other runtimes can stretch well past this) is pretty impressive, but in a chain of calls multiplied up it adds up fast. Using this with autoscaling to try to get ahead of predictable usage patterns, looks potentially useful, I think. With lots of separate Lambdas, using this to avoid cold starts on low-usage functions, I don't know, that $10 each adds up fast.