Firebird vs HSQLDB

Firebird is a free, open-source relational database management system with ANSI SQL features. It runs on Linux, macOS, and Windows, and supports self-hosted deployment. Its multi-generation architecture generally allows readers to access data without blocking writers. SQL features include stored procedures, triggers, common table expressions, cross-database queries, and flexible transaction management. A Trace API and monitoring tables support real-time monitoring, SQL debugging, and auditing. Security controls include users and roles, GRANT and REVOKE permissions, and a database owner concept; Windows Trusted Authentication can integrate with Windows domain or Active Directory security. Deployment choices include embedded, SuperServer, SuperClassic, and Classic architectures. Backup options include online backups and dumps, as well as incremental backup with partly supported point-in-time recovery. Drivers include Java JDBC,.NET, Python, ODBC, PHP, Delphi, and C++ Builder. Free community support is available through mailing lists, alongside commercial and special support. Firebird lists versions 5.0.4, 4.0.7, and 3.0.14 as latest in their series; versions 2.5 and earlier are discontinued and no longer maintained. The enterprise subscription is €199 a month, billed from €199/month/1 servers.

HSQLDB is a Java-based relational database engine for embedded or server use, with both in-memory and disk-based tables. It supports SQL:2023 core features and many optional features, plus lock-based and MVCC transaction models; the engine is fully multithreaded. Listed capabilities include JSON constructor functions, CSV loading and unloading, temporal system-versioned tables, row-level access control, and log-based replica synchronization. It includes a command-line SQL tool and simple GUI query tools. The latest official release listed is version 2.7.4, compatible with JDK 8 and above, and packages include Java 11 module jars as well as Java 8 jars for HSQLDB and SQL Tool. HSQLDB is self-hosted, with high availability, read replicas, and JSON data support listed. Its default combined limit for CACHED tables is 8TB, extendable to 256TB with a connection property; each TEXT table is limited to 256GB, and memory tables depend on available memory. The software is free to use in commercial products when license terms are met; its licenses are based on the new BSD License. The HSQLDB plan is free. A Developer subscription is $100 a year; Premier Corporate is $2,500 a year at the base level. Support options include community channels and paid commercial support.