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'll 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'll 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'll 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
10+ years of professional software engineering experience, with at least 2 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'll 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.