Registration (User Location) is an important part of a SIP infrastructure, eg: where to send a call for a particular user. During this presentation we'll learn how to scale FreeSWITCH capabilities so to handle high volume / high frequency transactions by having a mid-registrar absorbing the most transactions and only bother FreeSWITCH with the bare minimum info it needs (is the user reachable, and where). Multiple parallel calls can be "forked" if the user is registered as present at various devices (eg: deskphone and smartphone app), push notifications can be sent to "wake up" the user's app. We'll use OpenSIPS as an example of mid-registrar, but the same concepts and techniques can be implemented by any open source SIP proxy, like Kamailio, Repro, etc.