query optimization Archives

Mastering MongoDB Indexing: ESR Rule and Query Profiling with explain()

October 10, 2026

Slow MongoDB queries usually trace back to misplaced compound index keys and expensive in-memory sorts. Learn how to profile query execution plans with explain() and apply the Equality, Sort, Range (ESR) rule to cut query latency from seconds to milliseconds.

Database

SQL Refactoring: How to Convert Nested Subqueries to CTEs for Better Performance and Readability

September 14, 2026

Deeply nested SQL subqueries are hard to read, debug, and maintain. This guide shows you how to convert them to Common Table Expressions (CTEs) step by step, with real before/after examples and performance verification tips for PostgreSQL and MySQL.

Database

PostgreSQL Performance Analysis with pg_stat_statements: Find and Fix Slow Queries

May 25, 2026

pg_stat_statements is a built-in PostgreSQL extension that tracks aggregated execution statistics for every query — total time, call count, cache hit rate, and more. This guide walks through enabling it, querying the data to find your worst bottlenecks, and turning those stats into concrete index and query optimizations for production.