AI Engineer

Runna; City Of London; Hybrid; GBP 60,000 - 80,000; Full time

Job summary

A dynamic technology firm in London seeks an AI Engineer to develop AI-powered features that enhance training experiences for runners. The ideal candidate will work with large language models to deliver personalized insights and collaborate within a cross-functional team. Flexible working, benefits like health insurance, and a competitive salary package are offered.

Benefits

Flexible working

25 days holiday

Runna subscriptions for friends

Strava membership

Headspace membership

Gear and gym vouchers

Private health insurance

Mental wellness platform access

Fertility support benefits

Qualifications

• Solid experience working with LLMs in production.
• High-quality solutions that are maintainable and scalable.
• Experience writing production quality Python code.

Responsibilities

• Building AI-driven features using LLMs to enhance training experiences.
• Working across full stack of applied LLM engineering.
• Designing and refining prompt strategies and RAG pipelines.

Skills

Designing and building AI powered systems

Analytical and detail-oriented

Excellent communication and collaboration skills

Proficiency in Python

Tools

LLMs

Python

Cloud experience, ideally AWS

Job description

Overview

We're putting together a talented team to build the #1 training platform for Runners. We help everyday runners become outstanding by building an incredible app providing world-class training, coaching and community for everyone, whether you're improving your 5k time or training for your first marathon. In November 2023 we closed a $6.5M funding round led by JamJar with participation from Eka Ventures, Venrex and Creator Ventures. In 2024, we were selected by Apple as one of three global finalists for the 2024 iPhone App of the Year, reflecting the innovation and impact of what we0bve built and in 2025 we have just been acquired by Strava.

Our ambition is huge: to become the go-to global leading training platform for millions of runners everywhere. We0bre growing with purpose and looking for people who want to build something meaningful with lasting impact. With the recent acquisition by Strava accelerating our journey, now is a really magical time to join.

The Team Youll Join

As a cross functional (engineering, product, design, coaching) team of >20, the Train Team work at the heart of Runna's mission: delivering the best training possible to hundreds of thousands of runners worldwide. From creating and dynamically adjusting optimal, personalised training plans at scale, to analysing performance data to make training adjustment recommendations, to providing insight to users derived from their training and environment - we do it all.

What You'lle Be Doing

You'll be building AI-powered features that leverage large language models to transform the running experience for users around the world. As part of this work, you'lll be working closely with the engineering, product and coaching teams to build components that use LLMs to interpret, generate and personalise training insights - whether through conversational interfaces, knowledge-based reasoning or dynamic content generation. You'lll be part of the Train team here and we'll all support you along this exciting journey!

As an AI Engineer your role will include

• Building, testing and delivering new AI-driven features that use LLMs to enhance our personalised training experience, including conversational coaching, dynamic feedback, and content generation for hundreds of thousands of active users
• Working across the full stack of applied LLM engineering - from prompt design and model evaluation, to orchestration, deployment and iteration
• Keeping up to date with developments in the AI space, frontier models, new releases and entrants etc and ensuring we (the whole of engineering) are best utilising the latest approaches, models and strategies
• Designing and refining prompt strategies and retrieval-augmented generation (RAG) pipelines to ensure grounded, accurate and context-aware outputs
• Collaborating with coaches to help translate deep training knowledge into scalable, intelligent systems powered by AI
• Applying a data-driven and experimental approach to model development, evaluation and continuous improvement of LLM-based features - such as designing and implementing robust evaluation frameworks to measure LLM output quality, factuality, usefulness, and safety - both via automation and human feedback
• Experimenting (e.g. A/B tests in production) in order to ensure high quality outcomes
• Writing clean, well-tested Python code and contributing to the backend systems that support model orchestration, inference and integration into user-facing features

Requirements

What You'll Bring To The Team

We encourage applications from individuals with a range of experiences and backgrounds. Even if you don't meet every qualification listed, we'd love to hear from you and are open to tailoring roles to fit the right candidates. Please apply directly below or contact us for more information and to discuss your fit!

• Designing and building AI powered systems - you have solid experience working with LLMs in production
• Testing your code to ensure high quality solutions that are maintainable and scalable
• Analytical and detail-oriented, with a commitment to producing high-quality work
• A pragmatic mindset, with excellent communication and collaboration skills
• Proficiency in Python (object orientated) programming, with experience writing production quality code
• Enthusiasm for our ways of working which include
• Working within a highly-skilled engineering team in a fast-paced, iterative environment
• Iterative development, continuous deployment and test automation
• Knowledge sharing, pair programming, collaborative design & development
• Shared code ownership & cross-functional teams

Bonus Points If You Have

• An understanding of deployment, release cycles or CI/CD
• Exposure to delivering features end-to-end, from architecture design and building through to releasing, testing and supporting
• Experience with serverless and event driven architectures
• Cloud experience, ideally AWS
• A strong interest in the health/fitness technologies
• Some typescript experience

Benefits

Salary and Benefits

We'0bre offering a salary of £60k-£80k per year, depending on experience, plus participation in Strava's long-term incentive (stock) programs. Overview of our benefits is below:

We're also committed to continually evolving our benefits to support you as we grow. Here is a brief overview what we currently offer in the UK GB

• Flexible working - we typically spend 3 days a week together in our Vauxhall office
• 25 days holiday, plus bank holidays (which you can take whenever suits you)
• Runna subscriptions for you and 5 of your friends (get ready to be your friends fave person or save them for xmas presents!)
• Strava membership!
• Headspace membership
• Money every year to spend on gear, events and the gym!
• We'll give you a voucher to spend on our website so you can buy yourself new Runna kit (and will renew this every year on your work anniversary)
• Private health insurance with Bupa and workplace pension scheme
• Modern Health is a mental wellness platform and app that combines technology with professional support to improve mental well-being and reduce stress
• Carrot fertility support - this benefits provider can provide inclusive fertility, hormonal health, and family-forming benefits to our global employee population and takes the burden off what we know can be a stressful process.

Please see more info on our amazing benefits here: Benefits at Runna

Our Interview Process

Our aim is to keep the interview process as straightforward and enjoyable as possible, and will consist of the following stages:

1. Introductory chat (45 minute video call - intros; chat about experience; live coding)
2. Take Home Technical Task (~1-2 hours to complete)
3. Technical interview (75 minutes - the first half of the call will be used to discuss the take-home technical task from the previous stage and the second half will be some general architecture/tech questions)
4. Meet the team and in-person chat (in-person chat with different people in the team and some technical discussion)

Please let us know if there's anything we can do to better accommodate you throughout the interview process - this can be from scheduling interviews around childcare commitments to accessibility requirements. We want you to show your best self in the process, so please speak to your Talent Partner!

How to Apply

Please apply through this link (this will take you to our Workable career hub). Please note, we are unable to accept any applications outside of Workable. If you have any questions regarding the status of your application, please email [e-mail]

Still have questions or want to know more? Check out our Careers Page

We\'re unfortunately unable to sponsor for this role