Senior Backend Developer

Company

We are a Berlin-based B2C fintech operating in stealth, founded by two repeat founders (YC alum, exit) with prior 10+ year careers in investment banking and strategy consulting, respectively. We recently raised investment to assemble a 15 people, exceptionally strong core team.

Our culture is built on ownership and clarity. We align with you on vision, then set KPIs and required resources together—and then trust your drive and expertise.

The Opportunity

As a Senior Backend Developer / AI Engineer, you will work alongside our CTO on building and evolving our AI-powered fintech product. The core architecture is in place, providing a solid foundation to build upon as we integrate advanced LLM capabilities, establish AI pipelines, implement intelligent automation, and ship production-ready AI features. You'll be instrumental in shaping how we leverage AI to transform financial services, with significant autonomy to design and implement cutting-edge solutions.

What you will work on on daily basis

• Designing and implementing LLM-powered features and intelligent automation workflows
• Building robust AI pipelines with proper orchestration, error handling, and monitoring
• Developing RAG (Retrieval-Augmented Generation) systems for financial data processing
• Implementing and optimizing vector search and embedding strategies
• Creating evaluation frameworks for LLM outputs and maintaining quality standards
• Building prompt management systems and optimizing LLM interactions for cost and performance
• Integrating multiple AI models and managing model versioning/deployment
• Ensuring AI safety, reliability, and compliance in financial applications

Hard Requirements

• LLM Framework Expertise: Deep hands-on experience with , LangGraph for JavaScript, or similar LLM frameworks. You understand agent architectures, chain composition, memory management, and can build complex multi-step AI workflows in TypeScript/JavaScript.
• Workflow Orchestration: Production experience with Temporal .io (TypeScript SDK), Bull/BullMQ, or similar orchestration solutions. You know how to build reliable, long-running workflows with proper error handling, retries, and state management.
• Vector Database & RAG Systems: Proven experience implementing RAG architectures using vector databases (Pinecone, Weaviate, Qdrant, or pgvector) with clients. You understand embedding models, similarity search, and hybrid retrieval strategies.
• & TypeScript Mastery: Expert-level proficiency in and TypeScript with extensive experience integrating AI services (OpenAI, Anthropic, Cohere APIs). You're comfortable with streams, async patterns, WebSockets for real-time AI responses, and optimizing for latency.

Additional Technical Skills

• Experience with prompt engineering and prompt management systems accessible from
• Hands-on experience with AI model APIs and their SDKs (OpenAI, Anthropic, Hugging Face, Replicate)
• Knowledge of AI observability tools with integration (LangSmith, Helicone, or custom solutions)
• Proficiency with streaming architectures and Server-Sent Events (SSE) for real-time AI responses
• Understanding of AI safety, hallucination detection, and output validation techniques
• Familiarity with AI evaluation frameworks and automated testing of LLM outputs

Mindset & Approach

• AI-Native Thinking: You think in terms of probabilistic systems, understand LLM limitations, and know how to design robust systems around non-deterministic outputs.
• Pragmatic Innovation: You balance cutting-edge AI capabilities with production requirements—knowing when to use simple solutions vs. complex AI architectures.
• Ownership Mentality: You're proactive, resourceful, and accountable for your work—you don't wait to be told what to do.
• Team Player: You collaborate well with others, can explain AI concepts to non-technical stakeholders, and elevate those around you.
• Quality-Focused: You understand the importance of evaluation, testing, and monitoring in AI systems and build with observability in mind.
• Continuous Learner: You stay current with the rapidly evolving AI landscape, experiment with new models and techniques, and are energized by pushing the boundaries of what's possible.

Compensation & How We Work

• Competitive salary commensurate with experience (€80k-€110k+ depending on seniority)
• On-site in Berlin-Mitte, with flexible remote work as you see fit (typically 3-4 days in office, flexible on specific days)
• High autonomy, low politics, fast decision-making—we value impact over process
• Top-tier equipment—whatever tools you need to do your best work

We're an equal opportunity employer. We value diversity and are committed to creating an inclusive environment for all employees. If you're excited about the role but don't meet 100% of the criteria, we'd still love to hear from you—particularly if you bring unique perspectives or experiences that would strengthen our team.