Data should be saved in a database rather than in local json files

[martinlevesque]

The boards data are currently saved as json files as far as I can see. They should be saved using any database. And maybe there could be a mode without any persitence - everything streamed over WS.

[dazsmith]

Json has the advantage of very easy automated backup, server side.

[lovasoa]

yes, saving boards as simple files also has its advantages. Ideally, we would have several persistence backends between which the user could choose.

see #21