The JusDB Database Engineering Blog

Master MySQL 8.0 window functions for analytical queries. Covers ROW_NUMBER, RANK, LAG/LEAD for period comparison, running totals with SUM OVER, and NTILE quartiles.

Execute MySQL schema migrations safely with the expand-contract pattern, batched backfills, backward-compatible changes, and migration tooling comparison (Flyway, Liquibase, gh-ost).

ClickHouse MergeTree is why ClickHouse queries 1 billion rows in 0.3 seconds. Learn how parts, merges, and sparse indexes work, and how to choose the ORDER BY key, secondary indexes, and MergeTree variants.

Use MySQL JSON columns effectively with path operators, functional indexes via generated columns, JSON_CONTAINS filtering, and partial updates with JSON_SET.

Compare three PostgreSQL multi-tenant patterns: shared schema with RLS, schema-per-tenant, and database-per-tenant. Includes hash partitioning for shared schema at scale.

Implement least-privilege access in PostgreSQL with role hierarchies, ALTER DEFAULT PRIVILEGES, schema separation, and privilege auditing queries.

TiDB 8.0 is the most production-ready version of the distributed SQL database yet. With improved HTAP, stronger MySQL compatibility, and Resource Groups, it's compelling for teams outgrowing single-node MySQL.

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

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.

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.

Compare CockroachDB, Google Spanner, and YugabyteDB — consistency models, PostgreSQL compatibility, and operational costs

Understand Google Spanner's architecture — TrueTime, interleaved tables, schema design, and cost model