Which RDS database engine does AWS recommend for maximum compatibility with MySQL?

Correct answer: MySQL

Option B is correct because AWS RDS for MySQL is the native MySQL engine, providing full compatibility with MySQL features, syntax, stored procedures, and connectors without any translation layer. Option A (PostgreSQL) is a separate open-source engine with a different SQL dialect and feature set, not compatible with MySQL applications. Option C (MariaDB) is a MySQL fork that is largely compatible but has diverged in some features and internals, meaning AWS recommends MySQL itself for maximum MySQL compatibility. Option D (Oracle) is an entirely different commercial database engine with its own proprietary SQL extensions and is not compatible with MySQL workloads.