I'm trying to implement a system using node.js in which a number of sites would contain js loaded from a common host, and trigger an action when some user visits n+ sites.
I suppose a nosql solution storing a mapping of ip address => array of sites visited would be preferable to a RDBM both in terms of performance and simplicity. The actions I need are "add to array if not there already" and getting the length of the array. Also, I wouldn't like it all to sit in memory all the time, since the db might get large some day.
What's a system that fits these requirements the best? MongoDB seems like a nice option given $addToSet exists, but maybe there's something better in terms of RAM usage?
When I hear about working with lists or sets, the first choice is Redis