I started working with Pavel Durov in 2011 on the VKontakte Android app, after winning several of his developer contests, and it all just went from there. I was the last one of the "old" team to transfer to Telegram. My main job was actually the libtgvoip[1] library and its integration into the Android app (the other platforms were done by their corresponding devs).
I got fired in 2019 because the calls weren't working satisfactorily for Pavel. He got furious when he was unable to call some journalist, cursed at me in front of the entire team and sent me a termination notice. In hindsight, I should've definitely not taken building a VoIP library from scratch alone upon myself. It's a massive undertaking. But at least I learned a lot, and many people say that my implementation performed noticeably better than the current WebRTC-based one ¯\_(ツ)_/¯
I'm now working on two fediverse projects at the same time — Smithereen[2], a VK-like ActivityPub server, and the Mastodon Android app[3].
[1] https://github.com/grishka/libtgvoip
