Connecting members with external data

Hi. I’m using EE as a user front end to access data from a server app which I’m also authoring. The server app includes a large data set which doesn’t make sense to include within the EE environment. I do need to determine which EE members have access to which sets of this other data, so a logged-in EE user can view their info.

The exp_members table has two possible fields for this, member_id and unique_id. unique_id seems the better field as it’s a UUID (or close to it).

In my research I found several pages indicating the unique_id field was stored in a user cookie, but I’m not seeing that. I’m suspecting this was changed in 2.x. One example:

http://stackoverflow.com/questions/1279842/way-to-get-logged-in-user-in-expression-engine

Any suggestions or best practices here? Is unique_id safe?

Thanks!