HSQLDB

HSQLDB is a Java relational database engine that can run inside an application or as a server, using either memory-resident or disk-backed tables. It is best suited to Java teams that want a self-hosted SQL database with substantial standards coverage and deployment control. The principal appeal is a capable, freely usable engine; the cost is that your team owns operations unless it buys support.

Overview

HSQLDB combines embedded and server modes, making it useful for applications that need a local database as well as installations that centralize database access. Its new-BSD-based licensing permits commercial use and distribution when the license terms are met, so product teams can ship it without a per-database software charge. Self-hosting also means responsibility for deployment, maintenance, and capacity planning stays with you.

The engine dates to 2001 and remains particularly relevant where Java compatibility and an embeddable architecture matter. It is not a hosted service with managed infrastructure, so organizations seeking a provider-run database should look elsewhere.

Key features

SQL:2023 core support and an extensive set of optional features give HSQLDB considerably more SQL depth than a minimal embedded store. JSON data support, JSON constructor functions, CSV load and unload, temporal system-versioned tables, and row-level access control cover modern application and governance requirements. These capabilities reduce the need to bolt on separate handling for common data formats and history tracking.

Concurrency is configurable through lock-based or MVCC transaction models, and the engine is fully multithreaded. High availability, read replicas, and log-based replica synchronization provide a foundation for resilient deployments, although implementing and operating that architecture remains your responsibility. Memory tables are constrained by available RAM, while CACHED table data and indexes are written to disk, allowing larger working sets when persistence is more important than memory speed.

A command-line SQL tool and simple GUI query tools support development and administration. Named integrations include OpenOffice, LibreOffice, Spring, Hibernate, Flyway, Liquibase, DBeaver, and Eclipse, which should ease adoption in those ecosystems. Release 2.7.4 works with JDK 8 and newer; packages include Java 11 module jars and Java 8 jars for both HSQLDB and SQL Tool.

Pricing

The HSQLDB plan costs nothing and covers use and distribution under its licenses. There is no free trial because the core software is already free. This is the right tier for individuals, open-source projects, and commercial products that can handle their own support and comply with the license.

The Developer subscription costs $100 a year, billed as an annual subscription. It adds priority support and input into future development, making it suited to individual developers who need a faster route to answers or want a voice in the project. SupportWare Developer subscription is also $100 a year, billed at $100 annually, for individual developers seeking priority questions and development input.

Basic Corporate subscription uses custom pricing and is for fewer than 50 distributed units. Its SupportWare counterpart costs $500 a year, with billing stated as $500-$1000 annually, and targets corporations with limited internal use or fewer than 50 distributed units; it adds priority support and input on future development.

Premier Corporate subscription costs $2,500 a year on a base-level annual subscription. It is intended for large corporations and large-scale use or distribution, with full deployment support and enhancement requests. SupportWare Premier Corporate subscription has the same 2500.00 USD base-level annual price and adds deployment support and enhancement requests. These paid tiers buy assistance and influence, not a hosted database service.

Platforms

HSQLDB supports API, Linux, macOS, self-hosted, and Windows deployments. Its self-hosted model and Java runtime compatibility favor teams comfortable packaging and operating their own database. The FAQ states a default combined CACHED-table limit of 8TB, extendable to 256TB through a connection property; each TEXT table is limited to 256GB. Those ceilings are substantial, but teams should validate their schema and connection configuration before committing to very large datasets.

Who it's for

Choose HSQLDB for Java applications that need embedded operation, server mode, broad SQL functionality, replicas, or commercial redistribution under a permissive license. It also fits teams that value optional paid access to project support and development direction. It is a weaker fit for organizations that want a fully managed cloud database, automatic operations, or a non-Java-centered deployment approach.

Pros and cons

• Pros: Free commercial-capable licensing when terms are met; SQL:2023 core coverage with modern JSON, CSV, temporal, and access-control features; both embedded and server modes; lock-based and MVCC transactions; high availability, read replicas, and replica synchronization; broad Java and tooling integrations.
• Cons: Self-hosting leaves deployment and administration to your team; memory-table capacity depends on available RAM; paid support is needed for priority assistance, deployment help, or formal development input; very large deployments must account for CACHED and TEXT table limits.

Alternatives

SQLite is the simpler choice when you want a free embedded SQL engine with no separate server process and broad platform reach.

H2 Database Engine is another free embedded option, with source code included and no trial requirement.

Azure SQL Database suits readers who prefer a hosted, cross-platform service and a free offer with defined compute, storage, backup, and database quotas.

MySQL is worth considering for a familiar freemium database with a GPL-licensed Community Edition and replication and high-availability components.

InterSystems IRIS is a paid platform with a free Community Edition and trial for teams evaluating a broader commercial database product.

Microsoft SQL Server is an alternative for organizations aligned with Microsoft's editions and volume-licensing model.

Neon is a hosted option with a free tier defined by projects, compute hours, storage, branches, and egress.

C++Builder is a development tool alternative rather than a direct database-engine substitute.

Verdict

HSQLDB is a strong choice for Java developers and product teams that need a capable embedded or self-hosted relational engine without software licensing fees. Its standards coverage, transaction choices, replication features, and permissive commercial licensing are the main reasons to choose it. Look elsewhere if you want managed infrastructure or if your organization cannot take on database operations; paid subscriptions add support, but they do not change the self-hosted deployment model.