run <span style="font-family:monospace">ejabberd</span> on a cluster of machines and all of them will serve the same Jabber domain(s). When you need more capacity you can simply add a new cheap node to your cluster. Accordingly, you do not need to buy an expensive high-end machine to support tens of thousands concurrent users.</li><li class="li-itemize"><span style="font-weight:bold"><span style="font-size:large"><span style="color:#001376">Fault-tolerant:</span></span></span> You can deploy an <span style=