What are the collective communication operations (all-reduce, all-gather, reduce-scatter) in distributed training?
Distributed training is bottlenecked by GPU-to-GPU communication, and these collectives are how the data moves. The signal is what each one does and which parallelism strategy depends on it. Here is the answer.
Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.
Distributed training is bottlenecked by GPU-to-GPU communication, and these collectives are how the data moves. The signal is what each one does and which parallelism strategy depends on it. Here is the answer.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.