#sql

August 5th, 2026

The Query That Killed My Database: A Postmortem

A single SQL query took down production for twelve minutes. Here is the postmortem on how a correlated subquery with 200k posts became a database killer — and the exact fix that brought execution time from 4 minutes to 3 milliseconds.

June 20th, 2026

The Index You Think You Need Is the Index You Should Not Build

Indexes are not free — every write costs more disk I/O and space. Here is how to choose the right index type, order composite columns correctly, and use covering indexes to eliminate table access entirely.