The JusDB Database Engineering Blog

A top-down playbook for high-performance MongoDB: measure with the profiler and explain(), model for access patterns, index by the ESR rule, keep the working set in the WiredTiger cache, pool connections, and scale reads with secondaries and sharding — with flow diagrams for each layer.

A repeatable, top-down method for tuning PostgreSQL: measure with pg_stat_statements, read plans with EXPLAIN (ANALYZE, BUFFERS), fix queries and indexes before parameters, then tune memory, I/O, WAL, connection pooling, and autovacuum — with a ready-to-adapt postgresql.conf baseline.

Use hypopg to test how a new PostgreSQL index would affect query plans before building it. Includes install, hypothetical index creation, EXPLAIN workflow, and index sizing.

A critical bug in MongoDB 8.0 (SERVER-97368) affects TTL index behavior — causing documents to persist beyond expiration or delete prematurely. Here's how to detect and mitigate it.

Understand when MySQL JSON columns help and hurt performance. Learn functional indexes, JSON_TABLE, and when to migrate JSON to normalized columns.

Use MySQL 8.0 generated columns to index computed values, JSON paths, and date parts. Covers virtual vs stored tradeoffs and functional index patterns.

MySQL InnoDB full-text search is underused and often misconfigured. With 8.4 LTS, new defaults and tuning opportunities can cut FTS query time by 60% or more.

PostgreSQL offers multiple index types for different access patterns — and choosing wrong means slow queries or wasted space. A comprehensive guide to indexing strategy, from type selection to monitoring and maintenance.

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.

OpenSearch (Apache 2.0) and Elasticsearch (EL2/SSPL) have diverged. Compare licensing, security features, AI/ML capabilities, and migration complexity for 2026.

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.

Compare Elasticsearch, Typesense, and Meilisearch — relevance, speed, operational complexity, and when to use each