MySQL

The world's most widely deployed open-source relational database — the standard database for PHP applications, WordPress, and large-scale web platforms.

MySQL is the most deployed relational database in the world, powering WordPress, Facebook (historically), Twitter, YouTube, and the majority of PHP-based web applications. It is the M in the LAMP stack (Linux, Apache, MySQL, PHP) and MEAN/MERN stack variants, and remains the default database for shared hosting environments and many legacy enterprise applications. While PostgreSQL has overtaken MySQL in developer preference surveys, MySQL's installed base is enormous — knowledge of MySQL syntax, indexing, and query optimization is required for roles working with any PHP, WordPress, or legacy stack.

Typical time to job-readiness: ~4 weeks.

Learning MySQL

Beginner

MySQL syntax is nearly identical to standard SQL — if you know SELECT, JOIN, GROUP BY, and WHERE, you can query MySQL immediately. Install MySQL locally with Docker or MySQL Workbench and practice writing queries against a sample database like Sakila.

Intermediate

Index types (B-tree, full-text, composite), EXPLAIN for query analysis, stored procedures and triggers, and the differences between MySQL storage engines (InnoDB vs MyISAM). Learn how transactions and locking work — MVCC in InnoDB is critical for understanding concurrent write behavior.

Advanced

MySQL replication (primary/replica), binary log analysis, partitioning large tables, and query cache tuning. For WordPress-heavy roles, understand how to optimize the wp_postmeta and wp_options tables which are the most common performance bottlenecks. MySQL DBA interviews include backup/restore strategies and replication topology design.

Key concepts

  • InnoDB storage engine — default since MySQL 5.5; supports ACID transactions and foreign keys
  • Indexes: B-tree indexes on frequently queried columns; composite indexes for multi-column queries
  • EXPLAIN — shows the query execution plan; use it to identify full table scans and missing indexes
  • Transactions: BEGIN, COMMIT, ROLLBACK; InnoDB uses MVCC for concurrent reads without blocking
  • Replication: primary/replica topology for read scaling and failover
  • MySQL vs PostgreSQL: MySQL is faster for reads-heavy workloads; PostgreSQL has superior JSON and extensibility

Common interview topics

  • What is an index in MySQL and when would you add one
  • How does MVCC work in InnoDB
  • What is the difference between MyISAM and InnoDB
  • How would you diagnose a slow query in MySQL
  • Explain primary/replica replication — how does it work and what are its limitations

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