Senior Fullstack Engineer (m/f/d)

CLOUDYRION was founded in 2020, bootstrapped and built around a simple idea: cybersecurity done properly, by people who actually care.
We work with large enterprises in the telecoms, banking, insurance, automotive and critical infrastructure sectors. Our Secure by Design, Ethical Hacking and Secure Strategy Consulting services help them get security right from the ground up.
With our founder as CEO and free from investor influence, we are still upholding our values five years on: Fail fast and learn quickly. Be a ray of sunshine. Tear down those walls.
Working at CLOUDYRION means being part of a team who love what they do, embrace diversity and celebrate their successes together.
This approach has proven its worth: our team now consists of 35 people and generates an annual turnover of around €6 million.
Learn more
Insights from real-world projects, technical deep dives and our take on secure-by-design, cloud security and modern security architectures can be found on our blog ( https://cloudyrion.com/en/insights/ ) .
Authentic insights into our office life can be found on Instagram ( https://www.instagram.com/cloudyrion/ ) .
Let’s talk!

• YOUR MISSIONAs a Senior Fullstack Engineer, you are a core builder in our Research and Development initiative: an AI platform that automates security reviews at the architecture level. You spend most of your time on the backend – building AI-integrated services, async pipelines, and the APIs that power our research platform. You also build the surfaces through which our consultants work with AI output, turning probabilistic results into something people can genuinely trust.YOUR ROLE- Backend & API: Build and extend FastAPI endpoints, Celery task orchestration, PostgreSQL schemas, and GCS object storage; clean integration with the AI/ML pipeline.
• Data Flow Ownership: Design how the platform's data is stored, versioned, and served to the UI.
• Knowledge Approval Workflow: Design and extend the lifecycle layer for documents in the platform: data model, SLA tracking, escalation signals, and provenance metadata.
• Consultant-facing UI: Build the surfaces where AI output meets users: long running task UX, real time updates, and the path from polling to WebSocket/SSE streaming.
• End-to-End Delivery: Work with the AI team and an external UX designer to ship features from pipeline to UI – and own what works under the hood.
• Platform Reliability: Shape test strategies, structured logging, performance budgets, and the SDLC and agile practices the team needs as it grows.

• Must haves
• 5+ years of fullstack experience with production ownership of complex software – ideally including AI-integrated workflows
• Python and FastAPI at senior level: API design, request validation with Pydantic, structured errorr handling
• PostgresSQL: schema design, migrations, query optimizations, audit and versioning patterns
• Async at scale: streaming responses (SSE/WebSocket), bounded concurrency, retry strategy across nested boundaries, idempotent task design with Celery or equivalent
• React and TypeScript: state management (TanStack Query, Zustand or similar), data-driven UI for domain experts
• Production deployment: Docker, Kubernetes or equivalent, CI/CD, and observability tooling (Sentry, OpenTelemetry or similar)
• Product judgement: you know what fits the roadmap and you speak up when something doesn't
• Experience building SDLC and agile practices in a small team
• Strong English communication
• A real plus
• GCP experience: Cloud Run, GCS, Secret Manager, Vertex AI
• Vector search (Weaviate, pgvector or similar) or graph databases (Neo4j or similar)
• AI/LLM systems: eval frameworks, prompt versioning, regression on non-deterministic outputs
• Security engineering: authn/authz patterns, session management, secrets handling
• Test strategy: experience building testing practices systematically within a team
• Background in developer tools, data-heavy SaaS, or expert-facing products