Senior Rust Engineer (80–100%) at Threema AG in Freienbach, CH

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

Senior Rust Engineer Backend (80–100%)

The Role

We’re looking for a senior engineer to help design and build the core services behind our messaging backend. You will work on the systems that handle message delivery, real-time presence, and end-to-end encryption at scale. Most of our backend is written in Rust, and we’re expanding it further.

You will join a small team of engineers who care about correctness, performance, and keeping things simple. Expect to write production code, review other people’s code, and have a say in architecture decisions from day one.

What You Will Do

• Design and build backend services in Rust that handle high-throughput, low-latency messaging traffic

• Work on core infrastructure: message queues, delivery guarantees, connection handling, and storage layers

• Debug and optimize systems under real production load, not just in benchmarks

• Review code and mentor other engineers on Rust patterns and systems design

• Take ownership of a service end to end, from design through deployment and maintenance

What We’re Looking For

• More than ten years of professional software engineering experience, with at least two years writing Rust in production

• Solid understanding of concurrency, memory management, and systems programming

• Experience with distributed systems: what happens when a network partitions, a node dies, or a queue backs up

• Comfort working close to the metal when needed, whether that’s networking, storage engines, or protocol design

• Experience in working on scalable, low-latency, high-throughput systems

• Good communication skills: you will need to explain trade-offs to people who don’t write Rust

• A degree in computer science or equivalent experience; we care more about what you’ve shipped than where you studied

Nice to Have

• Experience with async Rust (Tokio or similar)

• Background in messaging protocols, telecom, or real-time systems

• Contributions to open source Rust projects

• Experience with encryption or security-critical systems

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.