— Writing —
Every team ships with the same lie: throw everything on the database and it'll handle correctness. Works at 50 writes/sec. At 5,000 writes/sec, every FK is a lock queue, every cascade synchronously deletes thousands, fsync becomes the clock. Why staging never catches it, ten places where the bill shows up, the cost curve of a hot FK, why cascades are dangerous, how to diagnose your bottleneck, and the enforcer+checker pattern senior teams use to move constraints off the database without losing correctness.
Why your connection pool config is probably wrong — and how to fix it with Little's Law, Kingman's Formula, and the process-to-core ratio. Includes a real-world banking system that had 640 connections but only needed 5.
A deep-dive into non-SARGable SQL with B-tree diagrams, real EXPLAIN output, and the exact rewrites — told through a gaming dashboard that went from 4,200ms to 2ms without touching the schema.
How similarity search works under the hood — and why naive brute-force collapses at scale.
What happens when your index outgrows your data — and how we fixed it without downtime in production.