Threema is the world’s best-selling secure messenger for both private users and businesses. Since 2012, we have been working tirelessly to ensure that our users can communicate freely without worrying about their privacy. Our growing user base includes millions of private customers and thousands of businesses and organizations from all over the world.

We are growing and looking for a new team member to join as a

WebRTC Engineer (100%)

The role

You'll join the team that owns our real-time media stack, including native clients, the web browser and our SFU infrastructure. You'll work on problems like keeping a 200-person meeting stable when half the participants are on hotel Wi-Fi, getting screen sharing to stay crisp at low bandwidth, and cutting join times so a meeting starts the moment someone clicks the link.

This is a hands-on engineering role with real ownership. You'll design features, dig into packet captures when calls go wrong, and help shape the architecture as we scale.

What you'll do

• Build and improve the WebRTC media pipeline across web, desktop and mobile clients, including audio, video, screen sharing and data channels.

• Develop and scale our Selective Forwarding Unit (SFU) and signaling services to support large meetings, webinars and breakout rooms.

• Tune congestion control, bandwidth estimation, simulcast and SVC layer selection so calls adapt gracefully to poor networks.

• Own call quality end to end: define metrics, build dashboards, investigate issues using getStats, RTC event logs and packet traces, and ship fixes.

• Work on NAT traversal and connectivity, including STUN/TURN infrastructure, ICE behavior and fallbacks for restrictive corporate networks.

• Collaborate with client, backend, security and product teams on features like recording, live captions, noise suppression and end-to-end encryption.

• Review code, mentor other engineers and help set technical direction for the real-time stack.

What we're looking for

• 5+ years of software engineering experience, with at least 3 years working directly on WebRTC or other real-time media systems.

• Deep understanding of the WebRTC stack: SDP, ICE, DTLS, SRTP, and how they fit together in practice.

• Experience building or operating an SFU or MCU, whether custom or based on open-source projects such as mediasoup, Janus, Jitsi, Pion or LiveKit.

• Solid knowledge of audio and video codecs (Opus, VP8, VP9, AV1, H.264) and their trade-offs.

• Strong skills in at least one of C++, Kotlin, Go or Rust, plus comfort with TypeScript/JavaScript for browser-side work.

• A methodical approach to debugging distributed, latency-sensitive systems where the root cause might be the network, the device or the code.

• Clear communication and the ability to explain complex media problems to people outside the team.

Nice to have

• Contributions to libwebrtc or open-source WebRTC projects.

• Experience with Insertable Streams / SFrame for end-to-end encrypted media.

• Background in audio processing (echo cancellation, noise suppression, AGC) or ML-based media enhancement.

• Experience running media infrastructure on Kubernetes across multiple regions.

• Familiarity with interoperability standards such as SIP or integrating with PSTN gateways.

What We Offer

• A young, motivated team with straightforward communication

• Flexible working hours, option to work from home up to two days per week

• Option to work from anywhere for two weeks per year

• Option to take unpaid leave

• You can choose your own hardware (macOS or Linux)

• Public transportation discount or parking space (electric car charging available)

• Free use of fitness room, including a fitness trainer once a month

• Professional massage once a month

• Internal German or English courses

• A great coffee machine ;-)

• Regular company events and aperitifs

• The good feeling of contributing to the effective protection of the privacy of millions of people

Place of work: Pfäffikon SZ (Greater Zurich Area)

Start date: Immediately or by agreement

Have we sparked your interest?

We believe that diverse teams build better products. We welcome and encourage applications from people of all backgrounds, and perspectives. Your unique experience is an asset, and we’d love to hear from you.

Applications sent via email cannot be considered. Please use the official "Apply" button below so we don't accidentally miss your resume in our crowded inboxes

For agencies: we are filling this role directly and do not accept unsolicited candidate profiles.