Code Room
System designHardsd-g709
Subject Storage engineLevel Senior–Staff~45 minCommon in Storage & CDN · Algorithms & data structures interviewsIndustries Technology, Software development

Question

Design an LSM-tree (log-structured merge) storage engine to back a write-heavy key-value store: ~500K writes/sec of 200-byte records, a 10:1 write-to-read ratio, point lookups and short range scans, and a strict durability guarantee that an acknowledged write survives a single-node crash. Walk through the in-memory and on-disk structures, how reads are served, and how background work keeps the engine healthy under sustained load.

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.

Narrate your design
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Run or narrate your approach, then ask the coach.