System designHardsd-g722

Subject Storage engineLevel Senior–Staff~40 minCommon in Storage & CDN · Algorithms & data structures interviewsIndustries Technology, Software development

Question

You run an LSM-based wide-column store (Cassandra/HBase style) and a high-delete, range-scan workload is misbehaving: a partition that holds a queue (rows inserted then deleted as they're processed) is getting slower and slower to scan even though it's logically near-empty. Design how the storage engine should handle deletes and range reads so this doesn't happen, and explain the underlying mechanics. Assume sustained writes plus deletes and frequent range scans over recently-touched partitions.

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.

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Narrate your design

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