Software Engineer - Fullstack & AI (m/w/d)

About the role

You will join a fast‑moving startup that aims to accelerate the energy transition in Germany. As a Fullstack & AI Software Engineer you will own feature development from concept to production, bridging backend services and a modern React UI while driving the company’s AI roadmap.

Key responsibilities

• Design, develop and ship end‑to‑end product features using Kotlin/Spring Boot on the backend and React/TypeScript on the frontend.
• Integrate large language model APIs (OpenAI, Gemini, Anthropic) and turn them into tangible product value.
• Build advanced agentic workflows, including tool/function calling, ReAct loops, multi‑step orchestration and memory systems.
• Collaborate with the Data Engineer to connect data pipelines to product features and contribute to CI/CD pipelines.
• Implement security best practices, focusing on prompt‑injection defence, output validation and data privacy.

Required profile

• Strong proficiency in Kotlin/JVM (Spring Boot, Hibernate) and solid Python experience (FastAPI).
• Hands‑on experience integrating LLM APIs and understanding of RAG, context management and reasoning patterns.
• Comfortable with PostgreSQL and basic knowledge of TypeScript/React/Redux.
• Security‑first mindset (OWASP Top 10) and awareness of LLM‑specific risks.
• Fluent English; German is a plus.

Required skills

• Kotlin
• Spring Boot
• Hibernate
• Python
• FastAPI
• React
• TypeScript
• Redux
• PostgreSQL
• LLM APIs (OpenAI, Gemini, Anthropic)
• LangGraph (plus)
• Google Cloud Platform
• CI/CD pipelines
• OWASP Top 10 security practices

What we offer

• Startup culture with high impact and direct influence on the founding team.
• Competitive salary package.
• Hybrid work model – remote flexibility combined with a Berlin office presence.
• Team off‑sites, office parties and a supportive development program with mentors.
• Opportunity to contribute to large‑scale CO₂ savings and the German energy transition.