WebRTC Engineer (100%)

Threema, the leading secure messenger used by millions of private users and thousands of organisations worldwide, is expanding its real‑time communications team. The opening is for a full‑time WebRTC Engineer who will become part of the group responsible for the media stack that powers native apps, browsers and the company's selective‑forwarding unit (SFU) infrastructure. In this hands‑on position you will design and enhance the WebRTC pipeline across web, desktop and mobile platforms, covering audio, video, screen sharing and data channels. You will develop and scale the SFU and signalling services to handle large meetings, webinars and breakout rooms, while fine‑tuning congestion control, bandwidth estimation, simulcast and SVC layer selection for unstable networks. Ownership of call quality will involve defining metrics, building dashboards, analysing getStats, RTC logs and packet captures, and delivering fixes. Additional duties include NAT traversal work (STUN/TURN, ICE), collaboration with backend, security and product teams on features such as recording, live captions, noise suppression and end‑to‑end encryption, as well as code reviews, mentoring and guiding the technical direction of the real‑time stack. The ideal candidate brings more than five years of software engineering experience, with at least three years focused on WebRTC or comparable real‑time media systems. A deep grasp of the WebRTC protocol suite, SDP, ICE, DTLS and SRTP, is essential, as is hands‑on experience building or operating an SFU/MCU, whether custom or based on open‑source solutions like mediasoup, Janus, Jitsi, Pion or LiveKit. Proficiency with audio and video codecs such as Opus, VP8, VP9, AV1 and H.264, and strong programming skills in at least one of C++, Kotlin, Go or Rust together with comfort in TypeScript/JavaScript, are required. The role also demands a systematic approach to debugging distributed, latency‑sensitive systems and the ability to communicate complex media issues clearly to non‑technical stakeholders. Additional assets include contributions to libwebrtc or other open‑source WebRTC projects, experience with Insertable Streams or SFrame for encrypted media, a background in audio processing or machine‑learning‑based media enhancement, and familiarity with running media infrastructure on Kubernetes across regions. Knowledge of SIP interoperability or PSTN gateway integration is also valued. The position is based in Pfäffikon SZ in the Greater Zurich Area, offering a young, motivated team, flexible working hours, up to two days per week remote work, a two‑week "work from anywhere" option, and a range of wellness benefits such as fitness facilities, monthly massages and public‑transport discounts. What the role asks for: - More than five years software engineering experience - At least three years WebRTC or real‑time media work - Deep understanding of SDP, ICE, DTLS, SRTP - Experience building or operating an SFU/MCU - Knowledge of Opus, VP8, VP9, AV1, H.264 codecs - Strong skills in C++, Kotlin, Go or Rust - Comfort with TypeScript/JavaScript for browser work - Methodical debugging of distributed latency‑sensitive systems - Clear communication of complex media problems - Nice-to-have: contributions to libwebrtc or open‑source WebRTC projects - Nice-to-have: experience with Insertable Streams / SFrame - Nice-to-have: background in audio processing or ML‑based media enhancement - Nice-to-have: running media infrastructure on Kubernetes across regions - Nice-to-have: familiarity with SIP or PSTN gateway integration