Dumb question. How is keeping a lambda warm different than just running a VM? Does the warm lambda instance respond quickly, and when it starts getting saturated, then additional Lambdas come online via a cold start process?
But what devoutsalsa said is true, you will still get a cold start when a request comes in while the already "warm" lambda is processing another request. This is one of the gotchas that not everyone seem to understand about these cloud functions. Sure, you'll scale quite horizontally, but just one executor at the time. If you have a long cold start, this can significantly increase latency. Some providers let you pay for concurrency, so that you can scale out more quickly.
