[zerox7felf]

Multimedia VoIP for hard of hearing / deaf-blind :) Working on a platform matching deaf video / text callers to interpreters, who then dial out to PSTN (phone network). Granted there is some web-stuff involved (one of the clients involved is Web-RTC), but it is mainly VoIP protocols among non-web or even 3rd party clients.

Working with a stateful and complex protocol like SIP is fun and a pain. You need stateful load balancers, traffic routing can be tricky (f.ex. in k8s...), interoperability between providers is not trivial, etc.

We also use relatively niche protocols for real-time text over RTP, which isn't (or until recently, hasn't been) supported in much VoIP software. This is starting to change due to EU legislation requiring accessibility in all commercial PSTN services, however.

The market for this type of tech was very small ~15-20 years ago. Thus, the company was comitting to every possible sales lead, leaving a right mess in tech debt. So much of the work is handling and working around that...

Much of the product pre-dates viable, affordable 3rd party technology, so there are home-grown components for all sorts of things: conferencing media component that also supports text, RTP proxies that were needed because few 3rd party clients supported ICE or TURN, etc.

Stateful and complex protocols, with home-grown bespoke software components, 3rd party interoperability, 15-20 years of technical debt, and changing customer demands. Fun and challenging!