Senior Software Engineer – Backend (Ai)

Womentech Network; Greater London; Hybrid; GBP 90,000 - 140,000; Full time

Benefits offered by this job

Equity

Competitive salary

28 days holiday

Hybrid work model

Flex days

Strong engineering culture

Job summary

Personio's AI-focused backend role in London invites a strong backend engineer to design and scale backend services powering the AI Assistant and agent experiences. You will work with ML engineers, own features end-to-end, and contribute to a fast-moving, architectural domain.

We value ownership, reliability, and collaboration across product and design while offering a hybrid model with two office days per week.

Qualifications

• Strong backend engineer with production experience.
• Proficiency in Kotlin/Java on JVM.
• Experience designing scalable APIs and distributed systems.
• Ownership mindset and strong cross-functional collaboration.
• Hands-on AI workflow experience and good judgment.

Responsibilities

• Design and build backend services and APIs powering AI experiences.
• Develop the platform for upcoming agentic products.
• Own features end to end from definition to production.
• Collaborate with ML engineers on retrieval, prompting, and model interaction.
• Make architectural decisions in a fast-moving domain.
• Work with Product and Design teams building AI features.

Skills

Backend engineer

Kotlin

Java

JVM

APIs design

Distributed systems

Ownership

Communication

AI fluency

Tools

AWS

Bedrock

Job description

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 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 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, we're building the People Operating System for Europe.

You'll be joining a high‑growth, product‑led company where engineering plays a central role in shaping the business. AI is one of the most visible parts of that, and this team sits at the centre of it.

What you can expect:

• Competitive salary and equity

• 28 days holiday, increasing with tenure

• Hybrid working model (2 days per week in the office)

• 20 Flex Days to work from anywhere in Europe

• A strong engineering culture focused on ownership and impact