Backend Engineer – AI Agents (all genders)

Lime Technologies; Köln; Hybrid; EUR 90,000 - 120,000; Full time

Benefits offered by this job

Health budget

Urban Sports Club subsidy

Learning budget

Udemy/Masterclass access

Leadership programmes

Weekly FIKA and team events

Cologne office 3 days / remote 2 days

Job ticket / mobility budget

Company pension via Zurich

28 days holiday + holidays off

Job summary

Lime Technologies in Cologne seeks a backend expert to advance AI features and automation, collaborating closely with Product. You will develop AI agents, shape the AI architecture, and ensure flexible work with various LLMs.

Expect to push QA with evals on real conversations, and to connect agents to knowledge via APIs, tools, and web crawling. German and English fluency are required; hybrid office setup in Cologne with on-site days and remote work.

Qualifications

• Five years backend experience with AI features.
• Proficient in Python; Django preferred.
• Experience building AI agents with context windows and tool calling.
• Familiar with RAG and vector databases.
• Experience with evals tools (Langfuse, Arize Phoenix, LangSmith) or self-built.
• Nice-to-have libraries like Pydantic AI or LiteLLM.
• Fluent in German and English.

Responsibilities

• Own backend AI features and collaborate with Product.
• Develop AI agents and automation such as Connect AI.
• Shape AI architecture for flexible multi-LLM work.
• Improve QA with evals on real customer conversations.
• Provide agents knowledge via APIs, MCP tools, and crawling.

Skills

Python

Django

AI feature development

Language model integration

Context windows & tool calling

Tools

Langfuse

Arize Phoenix

LangSmith

Pydantic AI

LiteLLM

Vector databases

Job description

What You'll Be Working On

• Within the backend team, you're the go-to person for AI and work closely with Product.
• You further develop our AI agents and automation solutions such as Connect AI, from the agent loop and tool calling to context management.
• You help shape our AI architecture and make sure we can work flexibly with different LLMs.
• When it comes to quality, we rely on evals with real customer conversations and methods like LLM-as-a-judge. You help expand this area so every new version gets measurably better.
• Through APIs, MCP tools and website crawling, you give our agents the knowledge and tools they need.

What Makes You a Fit

• You have at least five years of backend experience, including one year building AI features based on language models that people use every day.
• Python is your tool of choice, and ideally you already know Django.
• You've built AI agents before and know context windows, tool calling and prompting from hands-on work.
• You've worked with RAG and vector databases yourself.
• You're familiar with evals, whether with Langfuse, Arize Phoenix, LangSmith or something you built yourself.
• Libraries like Pydantic AI or LiteLLM are a plus.
• You follow what's happening in AI, try things out quickly and take ownership of your topics.
• You're fluent in German and English.

What’s in It for You

HEALTH & SPORTS

• 600 € health budget per year, including 24/7 medical advice — also for family members in your household
• Subsidised Urban Sports Club membership (20 € monthly contribution)

DEVELOPMENT & GROWTH

• Learning budget for courses, books and conferences
• Free access to Udemy, Masterclass and language learning apps
• Leadership programmes such as "Next Gen" and "Effective Manager"

TEAM & CULTURE

• Weekly FIKA, movie nights, book club and regular get-togethers and team events
• International summer party together with our colleagues in the Nordics

WORK ENVIRONMENT

• Office-first setup: 3 days in our Cologne office at the MediaPark, 2 days remote
• 360° view across Cologne from the 14th floor
• Workation within the EU
• Snacks, cereal bar and drinks in the office

COMPENSATION & BENEFITS

• Company pension scheme via Zurich with a 30 % employer contribution
• Job ticket or mobility budget, plus free parking at the MediaPark
• Corporate benefits
• 28 days of holiday, plus Christmas Eve and New Year's Eve off
• Up to 5 days of special leave for important life events