NoSQL systems are not SQL, but this does not mean they are unable to model relations. For instance in Redis you often have something like: user:1000 That

NoSQL systems are not SQL, but this does not mean they are unable to model relations. For instance in Redis you often have something like: user:1000 That is an hash with a few attributes, and among this attribs you can have 'group_id", that is an integer, for instance 50. Then if you access group:50 You have another data structure representing the group the user is associated with.