NoWDB is an experimental prototype for timeseries database with a graph-oriented datamodell. It supports a subset of SQL and supports stored procedures implemented as Lua scripts.
There are clients for C, C++, Go, Lua, Python and Julia. There is also a package providing server-side functionality implemented in Lua.
More documentation can be found here.
NoWDB is implemented in C99 and POSIX-compliant. It depends on: