docs: function (sid, session, callback) {
          var rec = {};
  
          // apply our properties:
          _applyProp(propSid, sid, rec);
          _applyProp(propData, serializer(session), rec);
  
          // opportunity to do:
          _applyProp(propLastActive, new Date(), rec);
  
          mongooseModel.findOneAndUpdate(_applyProp(propSid, sid), rec, {upsert: true}, function(err){
            (callback||_.noop)(err);
          });
        }