Exampel of how acking + controlled parallelism could look

[johanandren]

Here's a quick shot at doing ack:ing with configurable parallelism.

I think it brings at least one consequence to the surface that would never be acceptable in a real world app and that is that the entire request takes minutes to fulfill, even with an in mem journal and local http server for the twin. It could be a good idea to take a step back and consider either redesign to optimize for the top-level-all-levels-down case or disallow it down to some zoom level where you know it does not overwhelm the system (to not make it super easy for users to DoS the system).