Distributed filesystem metadata
Design the metadata service for a distributed filesystem (HDFS/GFS-style): the system stores huge files as fixed-size blocks replicated across thousands of data nodes, but a single namespace must track the directory tree, file→block mappings, and block→replica locations. Clients do path lookups, opens, and renames; the metadata layer must be fast, consistent, and not become a single point of failure. How do you design it?
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.