I'm looking at a live App Engine console for the Clojure app I'm working on right now, and I see cold-start JVM times varying from 3 to 10 seconds. Although this is a lot, with the latest App Engine, you can (1) pay $9/month to have 3 JVMs always running, and (2) your app receives warm-start requests which will cause a new JVM to start before it's needed.
In other words, your users should (almost?) never pay the penalty for a JVM cold-start. A single JVM stays around to serve requests as long as App Engine detects sufficient load to justify the resource usage.
In other words, your users should (almost?) never pay the penalty for a JVM cold-start. A single JVM stays around to serve requests as long as App Engine detects sufficient load to justify the resource usage.