Database Internals & Query Optimization: 100x Faster Queries

Most developers can write SQL but treat the database as a black box — so when a query is slow, all they can do is guess. This course opens the box. You'll learn how a database engine actually works, from the bytes on disk to the optimizer's decisions, and use that understanding to take real queries from seconds to milliseconds.

It's a visual, hands-on course built around side-by-side PostgreSQL 16 and MySQL 8 labs, interactive diagrams, and end-to-end performance case studies. Every concept is something you can see, measure, and reproduce.

What you'll learn

• Storage internals — pages and blocks, how rows are stored, heap vs clustered tables, fragmentation, and schema design for performance
• Memory — the buffer pool, cache eviction (LRU/Clock), measuring cache efficiency, and connection pooling
• Indexes — B-trees and B+ trees, clustered vs non-clustered, composite, covering, hash, bitmap, and specialized indexes, plus the real cost of indexing
• Query execution — the SQL lifecycle, query trees and operators, the Volcano and vectorized models, parallel execution, and plan caching
• Reading plans — EXPLAIN and EXPLAIN ANALYZE, cost estimation, scan types, and spotting bottlenecks
• The optimizer — statistics, cardinality estimation, histograms, join algorithms (nested loop, hash, merge), and join ordering
• Advanced optimization — sargable queries, predicate pushdown, query rewriting, materialized views, adaptive execution, and anti-patterns
• Transactions — ACID internals, isolation levels, locking, MVCC, and deadlocks
• Durability — write-ahead logging, checkpoints, crash recovery, and replication trade-offs
• Scaling — partitioning, partition pruning, sharding, distributed query processing, and read-scaling with caches
• In practice — engine-specific tuning for PostgreSQL, MySQL/InnoDB, and SQL Server, production diagnostics, and real-world case studies

What you'll do

Interactive widgets let you step a B-tree as it splits, watch the buffer pool evict pages, explore an EXPLAIN plan tree, and race a sequential scan against an index lookup. Hands-on labs and case studies walk the full optimization workflow on realistic problems — and the capstone has you run a documented optimization engagement end to end.

Who it's for

Developers, data engineers, and DBAs who can write SQL but want to understand why queries are slow and how to make them fast. Comfort with SQL is the only hard prerequisite — no prior systems-programming or database-internals experience required.