System designHardsd-g201

Subject ConsensusLevel Senior–Staff~50 minCommon in Databases & SQL · Distributed systems interviewsIndustries Technology, Software development

Question

Design the metadata/control plane for a distributed object store that must hold the authoritative mapping of buckets→shards→storage nodes (a few hundred GB of metadata, ~50k writes/sec of placement changes, millions of reads/sec). The mapping must be strongly consistent — two clients must never disagree on which node owns a shard — and must survive losing a minority of control-plane nodes with no data loss. How do you build it and how do you scale the read path without weakening consistency?

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.

Learn the concepts

Narrate your design

Loading whiteboard…

Run or narrate your approach, then ask the coach.