The JusDB Database Engineering Blog

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.

Master PostgreSQL EXPLAIN ANALYZE output: understand node types, cost estimates, actual vs estimated rows, and identify the root cause of slow queries.

AWS DMS can migrate terabytes of data with zero downtime — but default settings leave significant performance on the table. Here's how to tune DMS for production-grade migrations.

Decode MySQL deadlock messages from SHOW ENGINE INNODB STATUS, understand lock ordering, and write application code that eliminates deadlocks permanently.

Teams take down production for hours with migrations that could be zero-downtime operations. Learn to use gh-ost and CREATE INDEX CONCURRENTLY, implement rollback plans, and apply the expand-contract pattern for breaking changes.

Build selective, cross-version PostgreSQL replication with logical replication. Learn publications, subscriptions, conflict handling, and real-world use cases.

MySQL's foreign key implementation has evolved significantly from 5.7 through 8.4 — with changes to metadata locking, instant DDL interactions, and Group Replication behavior that every DBA needs to understand.

In 2026, more database versions are hitting end-of-life than any year in recent history.

Master InnoDB buffer pool internals: page management, chunk allocation, LRU algorithm, and tuning strategies for maximum cache efficiency.

Query remote PostgreSQL and MySQL databases from PostgreSQL with Foreign Data Wrappers. Covers postgres_fdw setup, IMPORT FOREIGN SCHEMA, and EXPLAIN pushdown verification.

Redis Sentinel and Redis Cluster both provide HA, but teams regularly choose the wrong one. Sentinel is simpler and covers 95% of use cases; Cluster is required for horizontal scale. Here's when to choose each.