Redis, Transactions and Throughput

Alright, it's been about 10 hours, and I still can't figure this out. Can someone please help? I am writing to both Redis and MongoDB each time my Node/Express API is called. However, when I query each database by the same key, Redis gradually starts to miss records over time. I can minimize this behavior by throttling the overall throughput (reducing # of ops I'm asking Redis to do). Here's the pseudo code:

function (req, res) {
  async.parallel {
    f {w:1 into MongoDB -- seems to be working fine}
    f {write to Redis -- seems to be miss-firing}

And here the Redis code:

var trx = 1; // transaction is 1:pending 0:complete
  async.whilst(function(){return trx;},
    function(callback){
      r.db.watch(key);
      r.db.hgetall(key, function(err, result){
      // update existing key
      if (result !== null) {
        update(key, result, req, function(err, result){
          if (err) {callback(err);}
            else if (result === null) {callback(null);}
            else {trx = 0; callback(null);}
          });
      }
      // new key
      else {
        newSeries(bin, req, function(err, result){
          if (err) {callback(err);}
          else if (result === null) {callback(null);}
          else {trx = 0; callback(null);}
        });
      }
    });
  }, function(err){if(err){callback(err);} else{callback(null);}}
 );

in the "update" and "newSeries" functions, I'm basically just doing a MULTI/EXEC to redis using the values from HGETALL, and returning the result (to ensure I didn't hit a race condition).

I am using Cluster with Node, so I have multiple threads executing at once to Redis. Any thoughts would be really helpful. Thanks.