Firebird and Lazarus
Firebird can point to a long-term development and has nevertheless remained slim. The basis for Firebird is Interbase in version 6. This story can be read here.
Firebird can be connected to other components come with Lazarus and also with ZEOS.
However, the benefits of interfacing with ZEOS are very good, in my opinion.
The most important information about Firebird can be found here:
Get to know Firebird in 2 minutes.
Why should you work with Firebird and Lazarus together?
The concept underlying Firebird and Lazarus originally comes from the same workshop. There is therefore a lot of experience and there are many forums for this configuration. Right now you realize that more and more developers use the combination Lazarus + Firebird. Many years of experience are behind this combination.
Firebird and Lazarus can be used completely free of license, also for commercial applications.
Firebird can be easily deployed as an embedded server without a database installation. As of Firebird version 3, this even makes multi-user operation possible, or several applications can access the embedded version at the same time.
In the server variants, databases can include 500 GB and more (how to secure them?).
The same program can then be operated in client server mode in a database installation with little customization. The Firebird client server has already proven itself in very large applications with more than one hundred users.
Firebird has a very active community and is constantly evolving.
Firebird supports ACID., Triggers, Stored Procedures and Events. Firebird runs on the 32- and 64-bit versions of Windows. Linux, Max OS X, HP-UX, FreeBSD, etc.
June 2019: Firebird 4.0 is now available as Beta-Release (RC 1) and can be connected with the beta-release of ZEOS 7.3 with Lazarus (here 2.0.4)