Here's my latest Nix-based project, quickdb (https://github.com/emmanuelrosa/quickdb)

Copy-pasting, ... quickdb is a suite of Nix packages to easily start development instances of PostgreSQL, MariaDB, or CouchDB on GNU Linux.

- Rootless

- The Nix package manager is the only dependency

- (somewhat) portable, because you can use nix-portable to build the packages.

- You can set up multiple instances of these databases by editing the config files to change the database port number.

- Database runs like a normal process you can kill with CTRL-C. This means the database runs when you want it to, and is not started automatically as a service.