The JusDB Database Engineering Blog

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

An honest comparison of MongoDB and PostgreSQL in 2026 — document model vs relational model, JSONB as a document store, ACID transaction trade-offs, horizontal scaling, licensing, and migration paths.

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

Choose Redis 8 or Valkey 8 from licensing, feature, managed-service, and operational requirements, then migrate within the documented compatibility boundary.

PostgreSQL 17 is one of the most impactful releases in years. Incremental backups, vacuum improvements, logical replication failover slots, and planner enhancements are all production-critical changes.

Aurora PostgreSQL offers sub-30-second failover and 15 read replicas but costs more per instance and adds per-I/O pricing. Learn when Aurora's HA wins over RDS simplicity with real cost modeling for 2025.

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

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

mysqld_exporter exposes 300+ MySQL metrics for Prometheus. Learn to deploy it, configure essential alerting rules for connection saturation and replication lag, and build production dashboards in Grafana.

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 flexible schema allows fields to be null, explicitly set to null, or simply absent — and these three states behave differently in queries, aggregations, and indexes.