Senior Full Stack Developer
Confirmed on the employer's own hiring board on Oct 11, 2026. First seen by Alion on Oct 2, 2026.
Join Thermosphr, a ClimateTech startup focused on optimizing energy management for commercial buildings across Europe. As a Senior Full Stack Developer, you will work closely with the CTO and other team members to build and maintain the infrastructure of our SaaS platform. You will take full ownership of the architecture and software development, ensuring stable and reliable real-time data flow between buildings and the cloud. This is an opportunity to make a direct impact on how we operate and scale while being part of an international team based in Paris and Berlin.
Missions
- Implement, maintain, and continuously improve a robust, scalable, and high-performance backend and cloud infrastructure.
- Take full ownership of architecture and software development across the full cycle, from prototype to production.
- Ensure stable and reliable real-time data flow between buildings and the cloud, including monitoring and alerting.
Profil recherché
**The position*** We're looking for a **fullstack software engineer**, with an interest towards **DevOps**, as we get increasingly growing needs in this aspect.
* You'll **take full ownership** across the full cycle, from prototype to production. Since we have no dedicated ops team, running your own services in production is part of the job. **No on-call**, though.
* You'll join a team **of two people** (Sylvain & Tim) in close collaboration with the CTO (Aaron).
**What you bring**
* Professional fluency in English (C1/C2);
* Senior-level mindset & experience developing back-end solutions in critical production environments;
* Advanced programming skills in **Python 3.12+**;
* Genuine experience with **GCP or equivalent** (AWS, Azure); or you're willing to learn and/or improve;
* Knowledge of **IoT**, or a **strong will to learn it**;
* Analytical and **critical thinking**; ability to take responsibility and ensure quality from prototype to production; ability to **say no**;
* **Fluency with AI-assisted coding tools** (Claude Code and similar), including the ability to **critically evaluate** AI-generated code and continuously improve internal procedures;
* Comfort with a **die & retry philosophy**: you try often, fail fast, and learn quickly (fail fast in dev, rigor in production);
* You stay ahead of the curve in software engineering and security, with a genuine interest in producing **battle-tested, production-grade code**;
* Entrepreneurial mindset: you find solutions, take initiative, and want to directly shape Thermosphr's product and direction (because **you will**).
**Bonus points**
* Familiarity with IoT, MQTT and/or building automation (HVAC);
* Networking knowledge: **routers, VLANs**;
* Ability to **challenge** existing architectures, including ones that have worked for years;
* (**True**) fullstack development experience (any framework, any language, ability to maintain a production fleet);
* Infrastructure as code with Terraform.
* You're curious. You're willing to learn. I've already said that. But we're all lifelong learners, after all.
Even if you don't tick all the boxes, we encourage you to apply!