How to associate User data with custom module? I'm thinking about a custom module where I need to save additional data (like user logs from other software, customer data, etc.) that'd go into a custom module user table.
How would I associate that with the user? Just the user ID?
Or is there anything else that I might want to save for uses that I might not yet know (Views, Domain Acess, Panels, Context, ...) or can I get all required data just be joining the UserID everywhere?
As usual there are plenty of ways to do something with Drupal.
Of course it would be possible to create a content type and import it via Feeds but sometimes (in case it might become plenty of data) it could be better to use a different approach.

So far it seems I'd go with MongoDB, the appropriate module and get the data into the DB using JSON and try to relate that to the current user if or where needed. Due to the amount of data and the visualisation it seems to be better to go the Document DB way.