> Let users write code how they want, its our job to make it work!

> Yes, but it's simply not safe to do this!

I think we need to offer our users a lot of stuff to get it right:

1. Tools so they know when a deploy puts in-flight invocations at risk, or maybe even in their editor, showing what invocations exist at each line of a handler

2. Nudge towards delayed call patterns whereever we can

3. Escape hatches if they absolutely have to change a long-running handler - ways to branch their code on the running version, clever cancellation tricks, 'restart as a new call' operation

Sadly no silver bullet. Delayed calls get you a lot of the way though :p