For personal stuff, I tend to keep it about as simple as possible with an HSQLDB instance hosted in-process. (All JVM/Clojure) I use a small library that encap

For personal stuff, I tend to keep it about as simple as possible with an HSQLDB instance hosted in-process. (All JVM/Clojure) I use a small library that encapsulates the use-case (including some schema migration stuff that should probably be replaced with flyway). https://github.com/mschaef/sql-file https://github.com/mschaef/sql-file There's a lot that can be said about this approach, both for and against, but I find that it brings a lot of power, is easy to set up, and generally stays out of the way. Given that the fundamental abstraction presented to user code is essentially SQL with connection pooling, there are also good escape strategies to get to architectures that would support however much capacity I'm ever likely to need.