Twilio, a telephony infrastructure web service “in the cloud”, allows web programmers to integrate real-time phone calls into their applications. But Twilio is not only a cloud-provider, but also a consumer of cloud services. In this talk, Jeff discusses how Twilio leverages commodity cloud services to build a scalable, reliable telephony service with almost purely variable costs. In particular, this variable cost model enables Twilio’s novel “Pay-As-You-Go” pricing, a drastic departure encumbants’ “per-channel,” long commitment pricing models.