Senior Full Stack Engineer GenAI Startup; f​/m​/d

Senior Full Stack Engineer for GenAI Startup (f/m/d)

Join to apply for the Senior Full Stack Engineer for GenAI Startup (f/m/d) role at Select Code GmbH

We’ve hit Product‑Market Fit. Our AI platform mein

GPT already serves 10k+ users across 250+ companies, and now we’re scaling. Your challenge:
Help us grow to 100k users.

Our mission with mein

GPT is to bring AI to the core of the SME sector. We’re building the central, all‑in‑one platform that makes powerful AI accessible to everyone. Your work will define how thousands of people interact with AI daily.

• Synchronize and index terabytes of client data and handle their permissions
• Process millions of LLM calls per month with high reliability
• Spawn thousands of code sandboxes per day that run scalably and securely
• Build the base infrastructure for our custom integrations team so new systems can be integrated in a few hours

• Own the most complex architectural problems within our platform, whether it’s optimizing our multi‑terabyte data synchronization or designing the next‑generation secure code sandbox infrastructure.
• Architect, build, and ship high‑quality, full‑stack features using React & Type Script, with a strong focus on long‑term scalability and user experience.
• Work with the development team to define technical roadmaps, align on architectural decisions, and ensure smooth, coordinated project execution.
• Shape our engineering culture by continuously improving development processes, code quality standards, and overall team performance.
• Debug production issues, identify root causes, and implement solutions to ensure a stable platform for users.
• Help mentor junior colleagues and improve our codebase through constructive, thorough code reviews.

• Context engineering:
  An AI agent is only as good as its context. The core challenge is assembling the perfect context in real‑time from multiple, diverse data sources to make the agent powerful and accurate.
• Scale:
  We process terabytes of sensitive customer data while fulfilling all requirements about performance, correctness, reliability, and security.
• UI/UX:
  The challenge is creating intuitive interfaces for new interaction patterns like real‑time streaming, live progress, and multi‑modal inputs (text, voice, image).

• 7+ years of professional experience in software engineering and mastery of our core technologies (React, Type Script, Postgre
  
  SQL) and surrounding ecosystem (Docker, CI/CD).
• Proven experience designing, scaling, and maintaining complex software architectures for high‑growth products.
• Strong sense of product ownership:
  You think beyond your own code and care about the big picture—how the product feels to users and how it succeeds as a whole.
• A passion for mentoring junior developers, improving codebase quality, and actively shaping our engineering standards & development processes.
• You are a quick learner and enjoy the fast pace and high‑growth environment that comes with a scaling product.

• Learn how to build a scalable AI platform, make critical product decisions in a high‑growth startup, and integrate cutting‑edge AI technology.
• Directly shape the product and its architecture during our critical 1M → 10M ARR growth phase. Your work will be used by thousands of users from day one.
• Enjoy flexible working hours with the option of 2 days/week in the home office.
• Further perks: access to 10,000+ sports facilities with the EGYM Wellpass, a €1,000 annual learning budget, and the Deutschlandticket.

• We use AI tools (Cursor, Claude Code, etc.) daily to be faster and smarter, but you remain in full control and responsible for your code.
• We minimize meetings and even make dailies optional to protect your deep work time.
• Healthy ambition:
  We have huge goals but are committed to a healthy work environment and make sure our people feel well.
• Fast delivery, close to the user:
  We ship fast, stay close to our customers, and let their direct feedback drive our next steps.
• Security & reliability first:
  As an enterprise platform, the security of customer data and…