Backend Engineer - AI Agents (all genders)

Lime-; Köln; Hybrid; EUR 75,000 - 110,000; Full time

Benefits offered by this job

Health budget

Urban Sports Club membership

Learning budget

Udemy/Masterclass access

Leadership programmes

Team events

Office in Cologne

Parking/transport benefits

Job summary

Lime- in Germany seeks a senior backend engineer to advance our AI features. You will work in the backend team, developing AI agents and automation, collaborating with Product, and shaping our AI architecture for flexible LLM integration.

You will implement evals, context windows, tool calls, and RAG, using Python and Django as core tools, ensuring German and English fluency for cross-team collaboration.

Qualifications

• 5+ years backend experience, incl. 1 year building AI features based on language models used daily.
• Proficient in Python with Django experience preferred.
• Experience building AI agents and understanding context windows, tool calling and prompting.
• Hands-on with RAG and vector databases.
• Familiarity with evals tools such as Langfuse, Arize Phoenix, LangSmith, or equivalents.

Responsibilities

• Develop AI agents and automation solutions like Connect AI, from agent loop to tool calls and context management.
• Collaborate with Product and backend teams to shape AI architecture for flexible multi-LLM work.
• Ensure quality through evals and real customer conversations, expanding assesment methods.
• Enable agents to access knowledge/tools via APIs, MCP tools, and website crawling.

Skills

Backend development

Python

Django

AI features

LLM tool calling

RAG

Vector databases

Langfuse/LangSmith

Pydantic AI

German & English

Tools

Connect AI

LLM integration

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