The JusDB Database Engineering Blog

MongoDB indexes fragment over time as documents are inserted, updated, and deleted. Here's how to detect fragmentation, measure its performance impact, and rebuild indexes safely.

Systematically diagnose and fix MySQL 'Too many connections' errors. Learn to identify connection leaks, tune wait_timeout, and implement ProxySQL pooling.

Use PostgreSQL EXPLAIN and EXPLAIN ANALYZE safely, interpret estimates and runtime evidence, and test the smallest change that addresses the real bottleneck.

Master MySQL performance optimization with this comprehensive 2025 guide. Learn expert techniques for query tuning, indexing strategies, memory configuration, and InnoDB optimization to achieve 10x database performance improvements.

MongoDB's indexing system supports single-field, compound, multikey, text, geospatial, and partial indexes. Choosing the right index type and key order determines whether your queries use microseconds or seconds.

MySQL transmits data in plaintext by default, exposing passwords and query results to network interception. Here's how to configure SSL/TLS for MySQL — from certificate generation to enforcing encrypted connections.

MySQL 8.0 introduced EXPLAIN FORMAT=TREE — a hierarchical, human-readable query plan format that reveals join order, access methods, and cost estimates in a way that the traditional tabular EXPLAIN cannot.

MySQL 8.0 introduced multi-valued indexes — allowing you to index individual elements of a JSON array so queries using MEMBER OF or JSON_OVERLAPS can use an index.

A production guide to zero-downtime database migrations — why ALTER TABLE causes downtime, the Expand-Contract pattern, safe migration patterns for PostgreSQL and MySQL, and tooling with Flyway, Liquibase, pt-osc, and gh-ost.

Detect query plan regressions in PostgreSQL using auto_explain, pg_hint_plan, and plan baseline management

Use pg_upgrade to migrate between PostgreSQL major versions — upgrade strategies, pre-checks, and rollback plans

ProxySQL pools thousands of application connections into a small backend pool, splits reads to replicas automatically, and lets you change routing without touching application code or restarting MySQL.