Fan-out + fan-in

Why you need it

Many backends need to start concurrent work and join on all results or a quorum.

Code examples

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# Start parallel Steps then wait for N channel messages / completions
# See design pattern: parallel and scalable-parallel.

Start multiple Steps (GoToMulti / multi movements) and wait on channels or step completion.

How Dex implements it

Dex schedules concurrent Step executions and joins via Channel conditions or WaitForStepCompletion.

Traditional workarounds

Hand-rolled: thread pools + Futures, or map-reduce job systems with custom join tables.