Subjects

Concurrency vs Parallelism

Untangle four words engineers constantly confuse: concurrency, parallelism, threads, and processes. Learn what runs truly simultaneously versus what merely interleaves, why Python's async model is single-threaded, and how getting this wrong causes real production bugs like sharing one database session across coroutines.

The CAP Theorem

Understand why distributed systems can only guarantee two of Consistency, Availability, and Partition Tolerance — and how real-world databases (Cassandra, Zookeeper, DynamoDB, Postgres) navigate this fundamental constraint.

Database Indexing

Learn how B-tree and hash indexes work internally, how the query planner uses them, when to create composite and covering indexes, and how to diagnose slow queries using EXPLAIN ANALYZE.