PostgreSQL

For applications demanding strong data consistency, transactional integrity, and the power of SQL, PostgreSQL (often called Postgres) is a highly regarded open-source object-relational database system. It's known as The world's most advanced open source relational database.

PostgreSQL offers robust ACID compliance, extensive support for standard SQL features, and numerous advanced capabilities, including complex query execution and support for various data types, making it suitable for critical systems.

Example: PostgreSQL is an excellent choice for the database backend of an e-commerce platform, ensuring that inventory levels, orders, and customer data remain consistent and accurate.