How to choose a broker for async work: comparing memory queues (Redis), AMQP brokers (RabbitMQ), and commit logs (Kafka) based on ordering, scale, durability, and operational cost.

How to handle thousands of incoming HTTP events per second: edge validation, buffering layers, batch writing to storage, and avoiding database connection starvation under spike load.

Learn how to read EXPLAIN and EXPLAIN ANALYZE, optimize JOINs and CTEs, implement keyset pagination, and understand database engine MVCC load behaviors.

How to optimize SQL and schema, choose index types, when database-side logic becomes a liability, how MySQL and PostgreSQL differ in production, and what vertical scale, replicas, decomposition, and sharding really cost.