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

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Discuss how to provide read-your-writes (session) consistency for clients in an eventually-consistent, multi-region key-value store. Describe client-side and server-side techniques (session tokens, sticky sessions, causal metadata, read repair) and their operational implications. Give an approach that balances latency and correctness for a global application.

MediumTechnical

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Explain the differences between physical (raw file) backups and logical (export/dump) backups. For a distributed application that spans multiple databases and services, how would you ensure a consistent snapshot across systems? Discuss trade-offs between coordination complexity and recovery simplicity.

EasyTechnical

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Describe caching strategies: cache-aside, read-through, write-through, and write-back. For each strategy explain how cache invalidation is handled and the typical failure modes that produce stale reads or lost writes. As an SRE, outline a resilient cache invalidation strategy for a distributed Redis layer used by an application that performs concurrent updates to related keys.

HardTechnical

0 practiced

Plan and describe a non-blocking schema migration for adding a populated column to a 50 TB partitioned table that is distributed across hundreds of nodes. Requirements: zero or minimal impact to online queries, controlled resource usage during backfill, safe rollback path, and preservation of replica consistency. Describe tools, orchestration, throttling, and verification steps.

EasyTechnical

0 practiced

Describe full, incremental, and differential backups and how filesystem snapshots differ from logical and physical database backups. Explain point-in-time recovery (PITR) using transaction logs and list common pitfalls (missing WAL segments, long restoration time, network bandwidth constraints). For each backup type indicate typical RTO/RPO expectations and when you would use that approach.

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