code: function get(sessionId, cb) {
          has(sessionId, (hasId) => {
              if (hasId) {
                  cb(sessionIdCache[sessionId]);
              }
              else {
                  cb();
              }
          });
      }
docs: What is the latest tracked information for the user? We get it from the local cache, if we have it, otherwise we fetch it from the database and record in the local cache