HSQLDB
HSQLDB (HyperSQL Database) is an open-source relational database management system written in Java, designed for embedding in Java applications or running as a standalone server. It supports SQL standards, ACID transactions, and in-memory or disk-based storage, making it lightweight and fast for development, testing, and small-scale deployments. It is often used as an embedded database due to its small footprint and ease of integration.
Developers should learn HSQLDB when working on Java-based projects that require a lightweight, embeddable database for prototyping, unit testing, or small applications, as it eliminates the need for external database servers. It is particularly useful in scenarios like desktop applications, mobile apps, or development environments where quick setup and minimal configuration are priorities, and it serves as a good alternative to heavier databases like MySQL or PostgreSQL for simple use cases.