Mysql

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Database Indexes in Practice: Clustered vs Secondary, Composite, Covering, and Why Your Index Is Ignored

How real database indexes work in MySQL InnoDB and PostgreSQL: clustered vs heap storage, UUID vs time-ordered primary keys, composite index column order, covering indexes and index-only scans, why the planner ignores an index, and what every index costs on writes, with an interview talk track.

~25 min read · Beginner → Senior · 7 diagrams