Lead Full Stack Developer

Thermosphr EO Solutions GmbH; Paris; Hybride; EUR 110 000 - 150 000; Plein temps

Résumé du poste

Thermosphr EO Solutions GmbH in Paris is seeking a senior engineering lead who will remain hands-on while guiding the platform's direction. You report to the CTO and work with two senior engineers, owning production services in a hybrid Paris-based role.

You will balance roughly 60% hands-on development with 40% lead responsibilities, shaping architecture, and aligning technical work with business goals.

Qualifications

• Fluent English (C1/C2) required; strong product judgment and ability to defend and drop requests.
• Senior experience leading backend systems in production, including tech lead responsibilities.
• Excellent frontend capability to ship end-to-end features without waiting for others.
• Proficient Python 3.12+; production-grade code in distributed environments.
• Experience with GCP/AWS or willingness to learn quickly; analytics and critical thinking.
• Familiar with AI-assisted coding tools and evaluate AI-generated code critically.
• Entrepreneurial mindset; comfortable with ambiguity and owning outcomes.

Responsabilités

• Build approximately 60%: implement, maintain, and improve a robust backend and cloud infrastructure; own architecture end-to-end from prototype to production; ensure real-time data flow with monitoring and alerting; reduce technical debt and consolidate the platform.
• Lead and align approximately 40%: translate business priorities into technical work; contribute to product direction; grow the team by defining needs and conducting tech interviews.

Connaissances

English fluency

Product judgment

Senior-level experience

Frontend experience

Python 3.12+

Cloud (GCP/AWS)

Analytical thinking

Responsibility

AI-assisted coding tools

Die-and-retry philosophy

Production-grade code

Distributed environment

Entrepreneurial mindset

IoT / MQTT familiarity

Full-stack capabilities

Terraform (IaC)

Outils

Claude Code

Terraform

Description du poste

Who this role is for

You are probably senior at a scale-up or a larger company today. You may have recently moved into a management track and found that you miss building, or you may be at the point where the next step is leading people and you want that step to come with code still attached.

This is that role. You lead, you set direction, you own the relationship with the rest of the business, and you stay hands‑on. If you want to run a large organisation, we are too small for you. If you want to stop being interrupted, this is the wrong role. If you want the scope of a lead without giving up the work, this is a good fit.

You are not being hired to stop writing code. The split is roughly 60% hands‑on engineering, 40% leading technically and aligning.

What you’ll do

Build (approximately 60%)

• Implement, maintain, and continuously improve a robust, scalable, 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.

• Lead the reduction of technical debt and the consolidation of our platform.

Lead and align (approximately 40%)

• Translate commercial and product priorities from the leadership team and internal stakeholders into technical work, and give an honest read on cost, risk, and sequencing before anything is committed. Write these down. Decisions here are made in short documents, not in meetings, and this bullet is most of what you will be writing.

• Contribute to what we build, not only how. Product direction here is shaped by the people closest to the system, and you will be one of them.

• Grow the team. You will define what we need, run technical interviews, make the call on candidates, and own whether people ramp up well.

The positionYou report to the CTO (Aaron) and work alongside two senior software engineers (Sylvain and Tim). You are the technical authority on the platform and the day-to-day lead for the team.We have no dedicated ops team, so running your own services in production is part of the job. There is no on-call rotation.This is a hybrid position based in Central Paris, 1-2 days per week on site. The alignment part of this role works better in person, and the people you will be translating for are here.What you bringProfessional fluency in English (C1/C2).Product judgment. You can tell the difference between a request and a requirement, and you have opinions about what should be built that you are willing to defend and to drop.Senior-level experience building and operating back-end systems in critical production environments, including a period as tech lead, lead developer, or the de facto technical owner of a small team.Working frontend experience. You do not need to be a frontend specialist, but you need to be able to ship a feature end to end without waiting for someone else, and to review frontend work credibly.Ability to explain technical subjects clearly to non-technical audiencesAdvanced programming skills in Python 3.12+.Real experience with GCP or an equivalent (AWS, Azure), or a clear willingness to get there fast.Analytical and critical thinking, the ability to take responsibility for quality from prototype to production, and the 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 and retry philosophy: fail fast in development, rigour in production.A genuine interest in producing battle-tested, production-grade code within a distributed environment, and in staying current on software engineering and security.Entrepreneurial mindset: you find solutions, take initiative, and accept that at our size responsibilities do not come in neat boxes.Bonus pointsFamiliarity with IoT, MQTT, or building automation (HVAC).Networking knowledge: routers, VLANs.Ability to challenge existing architectures, including ones that have worked for years.True fullstack experience (from prototype to production, any framework, any language) and the ability to maintain a production fleet.Infrastructure as code with Terraform.You are curious and willing to learn. So are we. Even if you do not tick every box, we encourage you to apply.