Databases and Data Persistence Questions

Thorough knowledge of how to store, model, and protect application data at scale. Evaluate trade offs between relational databases and nonrelational databases and select appropriate store types such as key value stores, document databases, column oriented stores, and graph databases based on access patterns. Design schemas and data models that balance normalization and denormalization, choose effective indexing strategies, and understand partitioning and sharding approaches for scaling. Explain transaction semantics and guarantees including atomicity, consistency, isolation, and durability and explain trade offs between strong consistency and eventual consistency in distributed deployments. Cover replication, leader election, multi region deployments, failover strategies, and mitigation of replication lag. Discuss query optimization and execution plans, secondary indexing, caching versus persistent storage, backup and restore strategies including point in time recovery, schema migration techniques, retention and archiving, and handling common failure scenarios and data corruption. Be able to justify database choice and design decisions with respect to latency, throughput, availability, consistency, cost, and operational complexity.