Database and Caching Strategies Questions

Understanding when and how to use persistent databases and in memory caching to improve application performance and scalability. Candidates should be able to explain read and write optimization patterns, basic indexing concepts, trade offs between consistency and availability, replication and sharding approaches, cache types and placement, cache invalidation strategies and time to live policies, and when an in memory cache such as Redis or Memcached is appropriate. Discussion should include common bottlenecks, monitoring and operational considerations, and how caching interacts with application correctness and latency.