&gt; It has been used to host chat room with more than 70,000 concurrent clients, scaled on 7 m3.large EC2 instances and one relatively small Redis server.<p>Knowing nothing about anything, 70k clients on 7 servers does not sound immediately very impressive. That&#x27;s roughly 10k clients per server, and this is 15 years after &quot;C10k problem&quot; was coined. Could someone comment if I&#x27;m missing something major here?