One synchronous job, 16k GPUs, and any single component can stall all of them. The blast-radius analysis interviewers want: which faults take down a rack vs the run, where the shared single points of failure hide, and how parallelism layout maps onto failure domains.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
One synchronous job, 16k GPUs, and any single component can stall all of them. The blast-radius analysis interviewers want: which faults take down a rack vs the run, where the shared single points of failure hide, and how parallelism layout maps onto failure domains.
This probes whether you see a training cluster as a stack of nested failure domains, not a flat pool of GPUs. The strong answer maps physical domains (GPU, node, rack, power, cooling, network tier, fabric manager) to their blast radius, then aligns the parallelism layout so a domain failure costs a recoverable slice rather than the whole job, and names the shared SPOFs (subnet manager, fabric manager, shared storage, head node) that defeat naive redundancy.
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