Database Scalability and High Availability Questions

Architectural approaches and operational practices for scaling and maintaining database availability. Topics include vertical versus horizontal scaling trade offs; replication topologies, leader and follower roles, read replicas and replica lag; read write splitting and connection pooling; sharding and partitioning strategies including range based, hash based, and consistent hashing approaches; handling hot partitions and data skew; federation and multi database federation patterns; cache layers and cache invalidation; rebalancing and resharding strategies; distributed concurrency control and transactional guarantees across shards; multi region deployment strategies, cross region failover and disaster recovery; monitoring, capacity planning, automation for failover and backups, and cost optimization at scale. Candidates should be able to pick scaling approaches based on read and write patterns and explain operational complexity and trade offs introduced by distributed data.

MediumSystem Design

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Design a cache invalidation strategy for a user profile service where most reads must be low-latency but writes should become visible to the user's next read within 500 milliseconds. Consider use of CDN, in-memory caches, pub/sub invalidation, and fallback strategies.

EasyTechnical

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Explain connection pooling for databases and how read-write splitting interacts with connection pools. Describe typical pool sizing heuristics, pitfalls with high connection counts (especially from serverless functions), and strategies to protect the database from connection overload.

MediumSystem Design

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System design: Design an architecture to serve product detail reads for a large e-commerce site expecting 100k reads/sec and 2k writes/sec across 3 regions. Describe database choices, replication strategy, caching, read/write splitting, consistency model, and how you will handle search or filtering on product attributes.

EasyTechnical

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Define sharding and explain the difference between partitioning and sharding in a database context. Give simple examples of horizontal partitioning, vertical partitioning, and when sharding becomes necessary versus using partitioning or indexes.

HardSystem Design

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Design a backup and restore strategy for a compliance-sensitive 30 TB database that must support frequent incremental backups, cryptographic integrity verification, point-in-time restore to any time within 30 days, and regular automated restore validation. Include backup encryption, key rotation, and retention policies.

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