What is a database connection pool and why is it needed?

A database connection pool is a set of pre-opened and ready-to-use connections to a database that an application can reuse to execute queries.

Why is a pool needed:

• Reducing overhead: opening a new connection to the database is a costly operation in terms of time and resources. The pool helps avoid constant opening/closing.
• Resource management: it limits the maximum number of concurrent connections, preventing database overload.
• Performance improvement: reusing connections speeds up query processing.

In Java, a connection pool is usually implemented through third-party libraries (e.g., HikariCP, C3P0) or built-in features in JDBC drivers.

Example of using HikariCP:

HikariConfig config = new HikariConfig();
config.setJdbcUrl("jdbc:postgresql://localhost:5432/mydb");
config.setUsername("user");
config.setPassword("password");
config.setMaximumPoolSize(10);

HikariDataSource ds = new HikariDataSource(config);

try (Connection conn = ds.getConnection()) {
    // Use the connection
}

Thus, a connection pool provides efficient and controlled use of database connections, which is critical for application performance and stability.