Which are common backend databases for web apps?

• A. Microsoft SQLServer, Oracle, and MySQL
• B. PostgreSQL, MongoDB, Redis
• C. Oracle, PostgreSQL, SQLite
• D. IBM Db2, Sybase, MariaDB

Answer: (A)

Web apps rely on a structured, transactional store to keep data consistent and easy to query. The most common back-end databases for this role are Microsoft SQL Server, Oracle Database, and MySQL. They are mature, widely supported across platforms, and have extensive tooling, driver ecosystems, and integration with popular programming languages and frameworks. They all use SQL, support complex queries, indexing, and ACID transactions, and offer scalable options like replication and clustering to handle growing web traffic. This broad vendor support and proven reliability make them go-to choices for many production web applications.

Other options mix in non-relational stores or specialized use cases. For example, document stores or in‑memory caches serve different needs than a primary durable relational database, and SQLite is typically used for embedded or low-concurrency scenarios rather than a full‑fledged, multi-user web app backend. While IBM Db2, Sybase, or MariaDB exist in the ecosystem, the trio of SQL Server, Oracle, and MySQL remains a highly common, widely deployed baseline for web application persistence.