Senior Software Engineer – Backend (AI)

Personio's intelligent HR platform helps small and medium-sized organizations unlock the power of people by making complicated, time-consuming tasks simple and efficient. Our team of 1,500 Personios is building user-friendly products that delight our 15,000+ customers and their 1.5 million employees. Ready to make an impact from day one?
Senior Software Engineer – Backend
Product, Technology & Design Full Time London
Personio's intelligent HR platform helps small and medium-sized organizations unlock the power of people by making complicated, time-consuming tasks simple and efficient. Our team of 1,500 Personios is building user-friendly products that delight our 16,000+ customers and their 1.5 million employees. Ready to make an impact from day one?
About the Role
We're hiring multiple Senior Backend Engineers into our AI team in London.
This team owns Personio's AI experiences end to end. That means the model layer (how we interact with Bedrock, prompt tuning, RAG), the platform underneath it (infrastructure, data flow, the APIs our LLMs are exposed through), and the customer-facing side (how users actually trigger and interact with these features).
Alongside the Personio Assistant, this team owns the agentic architecture that Personio's next generation of AI features will be built on. That includes the Analytics Agent launching this year, agentic experiences in Recruiting, and AI features embedded across Performance & Development and People Analytics, such as follow-up questions inside summaries and smart metrics on the analytics dashboard.
You do not need a machine learning background. Most of this work is building well-designed, reliable backend systems, and it is not fundamentally different from building any other API. What is different is who you build it with and what sits on top: you will work day to day alongside machine learning engineers, and the systems you build are what every agentic experience at Personio will run on.
If you are a strong backend engineer who wants real exposure to applied AI without moving away from engineering, this is a good place to do it.
What You'll Do
Design and build the backend services and APIs that power Personio's AI Assistant and agent experiences

Build out the underlying platform that upcoming agentic products across Personio will be built on

Own features end to end, from problem definition through to production

Work directly with machine learning engineers on the systems around retrieval, prompting, and model interaction

Make architectural decisions in a young, fast-moving domain where the patterns are still being set

Collaborate with Product, Design, and the teams building AI features into their own product areas

What We're Looking For
Strong experience as a backend engineer in production environments

Solid skills in Kotlin, Java, or a similar JVM language, and comfort picking up a new stack

Experience designing and scaling APIs and distributed systems where reliability and correctness matter

Comfort building from scratch rather than extending established platforms and internal tooling

A strong sense of ownership, and the ability to move things forward without a lot of scaffolding around you

Clear communication, particularly across engineering disciplines

AI Fluency: You have hands-on experience using AI to improve your workflow, and the sound judgment to know exactly when to rely on it and when to step in yourself.

Nice to Have
Experience working alongside machine learning or data engineering teams

Exposure to LLM-based systems, RAG, or agent architectures

Experience with AWS, and with Bedrock or a comparable model platform

Interest in AI-assisted development workflows

Locations & Working Model
This role is based in London .
We follow a hybrid working model with 2 days per week in the office . This team is building deliberately in London, so we are looking for people who can be part of that in person.
 
Why Personio
At Personio