The JusDB Database Engineering Blog

Day-to-day MongoDB replica set operations: adding/removing members, triggering elections, diagnosing replication lag, and managing oplog size.

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

Diagnose MySQL 8.4 InnoDB deadlocks from lock evidence, correct ordering and indexing, use SKIP LOCKED only for queues, and retry whole transactions safely.

PostgreSQL's pg_stat_activity view exposes every connection's state — but understanding what 'idle in transaction' means and why it's dangerous requires knowing the full lifecycle of a PostgreSQL backend process.

Hatchet transforms raw MongoDB JSON logs into actionable insights — surfacing slow operations, connection storms, and namespace hotspots that are impossible to spot in raw log files.

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

Go beyond basics with Debezium — handle schema evolution, manage connector offsets, and build resilient CDC pipelines

A deep dive into InnoDB locking — record locks, gap locks, next-key locks, how READ COMMITTED eliminates gap locks, diagnosing deadlocks with SHOW ENGINE INNODB STATUS and performance_schema, and prevention patterns.

Essential MySQL diagnostic queries every DBA needs. Quickly identify slow queries, lock contention, replication lag, memory issues, and connection problems.

A comprehensive guide to MySQL replication lag — why it happens, why Seconds_Behind_Master lies, how to measure accurately with pt-heartbeat, and how to fix it with multi-threaded replication and LOGICAL_CLOCK parallelism.

Avoid these common MySQL configuration mistakes that cripple performance. Learn proper buffer pool sizing, connection limits, and InnoDB settings for production workloads.

MySQL 8.0 exposes error logs through performance_schema.error_log — enabling SQL-based filtering by severity, component, and timestamp without grep-ing log files.