Database Fundamentals and Storage Engines Questions

Core principles and components of data storage and persistence systems. This includes storage engine architectures and how they affect query processing and performance; transactions and isolation including atomicity, consistency, isolation, and durability; concurrency control and isolation levels; indexing strategies and how indexes affect read and write amplification; physical versus logical storage and object, block, and file storage characteristics; caching layers and cache invalidation patterns; replication basics and how replication affects durability and read performance; backup and recovery techniques including snapshots and point in time recovery; trade offs captured by consistency, availability, and partition tolerance reasoning; compression, cost versus performance trade offs, data retention, archival, and compliance concerns. Candidates should be able to reason about durability, persistence guarantees, operational recovery, and storage choices that affect latency, throughput, and cost.

HardTechnical

45 practiced

Operating Cassandra, you observe huge numbers of tombstones leading to CPU spikes and compaction storms. Outline a root-cause analysis, immediate mitigations to stabilize the cluster, long-term schema and TTL/compaction changes, and a recovery plan to restore healthy read/write performance without unacceptable data loss.

EasyTechnical

78 practiced

List and briefly explain the SQL standard isolation levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, and SERIALIZABLE. For each level name at least one anomaly it prevents or allows and give a short example use-case where that level is appropriate.

HardTechnical

46 practiced

Explain and compare synchronous vs asynchronous replication in terms of write latency, durability guarantees, failover behavior, and split-brain risk. Also explain quorum-based synchronous replication and how network partitions affect correctness.

HardSystem Design

39 practiced

Design a cost-effective archival architecture for 10TB/day of audit logs with 7-year retention and occasional monthly access. Detail lifecycle policies, tiering choices (hot/warm/cold), indexing strategy for occasional queries, encryption, and procedures to verify retention and restores for compliance.

MediumTechnical

36 practiced

Explain the following isolation anomalies and show a minimal SQL example (two concurrent transactions) that would demonstrate each: dirty read, non-repeatable read, phantom read, lost update, and write skew. Indicate which SQL isolation levels prevent each anomaly.

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