code: function update(sessionId, info) {
          sessionIdCache[sessionId] = info;
  
          db.collection('trackedUsersCache').update({
              _id: sessionId,
          }, { $set: {
              info: info,
          }}, {
              upsert: true
          }, (err) => {
              if (errorHandler.dbErrorCatcher(err)) { return false; }
              return true;
          });
  
      }
docs: Adding the id and the information in the cache. If we already have it, we update it