katowulf

// assumes you add a timestamp field to each record (see Firebase.ServerValue.TIMESTAMP)
// pros: fast and done server-side (less bandwidth, faster response), simple
// cons: a few bytes on each record for the timestamp
var ref = new Firebase(...);
ref.orderByChild('timestamp').startAt(Date.now()).on('child_added', function(snapshot) {
  console.log('new record', snap.key());
});

hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs