Composite indexes, covering indexes, and when indexing hurts more than it helps.

Read EXPLAIN plans, fix slow joins, and write queries the optimizer can actually use.

Cache-aside patterns, TTLs, and invalidation for lower database load and faster responses.

An honest comparison of features, performance, and ecosystem to guide your decision.

When to normalize for integrity and when deliberate denormalization improves performance.

ACID properties, isolation levels, and keeping your data consistent under concurrency.

Scale reads with replicas, handle replication lag, and know when to shard.