ToroDB

ToroDB was a MongoDB proxy that stored the data in PostgreSQL or MySQL, written in Java. It is not developed anymore, and WeKan does not run on it — what is kept here is the historical setup and the note about what to use instead.

Directory	What is in it
PostgreSQL	The ToroDB + PostgreSQL compose file, its README, changelog and licence

Use FerretDB instead: it is the same idea — the MongoDB wire protocol on top of an SQL database — but maintained, written in Go, and it is what WeKan runs on by default.