CPaaS
Communications Platform as a Service — cloud APIs that drop SMS, calls and video into any app without you running telco infrastructure.
The idea is to hide everything a PBX, SMSC or SIP trunk once demanded behind an HTTP call. A developer who wants to send a verification code or ring a customer does a POST, and the provider handles interconnection, numbers and per-country compliance. Twilio popularised the model in 2008 and gave the category its name.
Competitors are many — Sinch, MessageBird, Vonage (formerly Nexmo), Infobip, Bandwidth — and margins thin, since the final cost is still set by the carrier's termination fee. The line against UCaaS (finished calling apps) and CCaaS (contact centres) is blurry; CPaaS is the building blocks, not the finished product.