Senior Machine Learning Engineer

Trainline; Greater London; On-site; GBP 110,000 - 160,000; Full time

Benefits offered by this job

Private healthcare

Dental insurance

Work from abroad policy

Share purchase plan

EV scheme

Flexible time off

Family-friendly benefits

Job summary

Trainline is hiring a Senior Machine Learning Engineer in the UK to design and deploy scalable ML models that power search, recommendations, and pricing across our rail platform. You will work with data scientists, software engineers and product managers to deliver high-impact ML solutions.

The role requires a strong background in Python, ML libraries, statistics, and experience in productionising models. A hybrid working model with competitive benefits is offered.

Qualifications

• Advanced degree in Computer Science, Mathematics or related quantitative field.
• Considerable experience productionising machine learning models such as predictive modelling or recommender systems.
• Strong proficiency in Python and libraries like Pandas, NumPy and Scikit-learn.
• Solid grounding in statistics with data extraction and feature engineering techniques.
• Experience with Spark, agile delivery methods and CI/CD practices.
• Familiarity with DevOps and MLOps tools like Docker, Terraform, MLFlow.
• Confident in influencing and communicating with both technical and non-technical stakeholders.
• Ideally exposure to cloud infra, NLP or large language models, GIS or transport sector experience.

Responsibilities

• Design and deploy machine learning models at scale with measurable business impact.
• Own end-to-end ML delivery lifecycle: data exploration, feature engineering, model selection, evaluation, deployment and maintenance.
• Work in cross-functional teams with data scientists, software engineers and product managers.
• Shape technical direction and make scalable architectural decisions.
• Collaborate with stakeholders to propose data products leveraging Trainline datasets and modern algorithms.
• Build tools and libraries to accelerate ML delivery and improve team workflows.
• Mentor less experienced engineers and contribute to a culture of learning and experimentation.

Skills

Cross-functional teamwork

Python

ML model deployment

Stakeholder influence

Statistical methods

Cloud exposure

NLP/LLMs exposure

Spark

CI/CD

MLOps tools

Education

Advanced degree in CS/Math or quantitative field

Tools

Docker

Terraform

MLFlow

Job description

About us

We are champions of rail, inspired to build a greener, more sustainable future of travel. Trainline enables millions of travellers to find and book the best value tickets across carriers, fares, and journey options through our highly rated mobile app, website, and B2B partner channels.

Great journeys start with Trainline

Now Europe’s number 1 downloaded rail app, with over 135 million monthly visits and £6.3 billion in annual ticket sales, we collaborate with 270+ rail and coach companies in over 40 countries. We want to create a world where travel is as simple, seamless, eco-friendly and affordable as it should be.

Today, we're a FTSE 250 company driven by our incredible team of over 1,000 Trainliners from 50+ nationalities, based across London, Paris, Barcelona, Milan, Edinburgh and Madrid. With our focus on growth in the UK and Europe, now is the perfect time to join us on this high-speed journey.

Introducing the Trainline Machine Learning and AI Team

Machine learning sits at the heart of Trainline's mission to help millions of people make sustainable travel choices every day. Our models power some of the most important parts of the platform, from search and recommendations across mobile and web, to pricing and routing optimisation, personalised experiences enhanced by generative AI, data-driven marketing, and AI agents that support our customers.

Our machine learning teams own the complete delivery lifecycle from ideation through to production, working closely with engineers, data scientists and product managers across the business to grow the understanding and impact of machine learning and AI throughout Trainline. As a Senior Machine Learning Engineer, you will bring deep technical expertise and sound judgement to some of our most complex problems, and will play a key role in shaping technical direction and influencing stakeholders across the business, while helping to raise the capability of those around you.

In this role as the Senior Machine Learning Engineer, you will

• Work within cross-functional teams alongside data scientists, software engineers, data engineers and product managers




• Design and deliver machine learning models at scale that create measurable impact for the business




• Own the end-to-end machine learning delivery lifecycle, including data exploration, feature engineering, model selection and tuning, evaluation, deployment and maintenance




• Shape technical direction for your area, making well-reasoned architectural and modelling decisions that stand up at scale




• Partner with and influence stakeholders across the business to propose innovative data products that make the most of Trainline's extensive datasets and the latest algorithms




• Build tools, frameworks and libraries that accelerate the delivery of ML products and improve team workflows




• Provide technical mentorship and support the development of less experienced engineers, without formal people management responsibility




• Take an active role in our AI and ML community, helping foster a culture of rigorous learning and experimentation

We'd love to hear from you if you have

• An advanced degree in Computer Science, Mathematics or a related quantitative discipline, or equivalent experience




• Considerable experience productionising machine learning models, with strength in an area such as predictive modelling, classification, regression, optimisation or recommendation systems




• Strong proficiency in Python and open-source data libraries such as Pandas, NumPy and Scikit-learn




• A solid grounding in statistical methodologies, along with data extraction, manipulation and feature engineering techniques




• Experience with Spark, agile delivery methods and CI/CD practices




• Familiarity with DevOps and MLOps tools and practices, such as Docker, Terraform and MLFlow




• Confidence influencing and communicating with stakeholders across technical and non-technical teams




• Ideally, exposure to cloud infrastructure, NLP or large language models (such as fine-tuning, RAG or agents), graph technologies, or experience in the transport sector or with geographic information systems (GIS)

More information:

Enjoy fantastic perks like private healthcare & dental insurance, a generous work from abroad policy, 2-for-1 share purchase plans, an EV Scheme to further reduce carbon emissions, extra festive time off, and excellent family-friendly benefits.

We prioritise career growth with clear career paths, transparent pay bands, personal learning budgets, and regular learning days. Jump on board and supercharge your career from day one!

We're operating a hybrid model and ask that Trainliners work from the office a minimum of 60% of their time over a 12-week period. We also have a 28-day Work from Abroad policy.

Our values represent the things that matter most to us and what we live and breathe everyday, in everything we do:

• Think Big - We're building the future of rail




• Own It - We focus on every customer, partner and journey




• Travel Together - We're one team




• Do Good - We make a positive impact

We know that having a diverse team makes us better and helps us succeed. And we mean all forms of diversity - gender, ethnicity, sexuality, disability, nationality and diversity of thought. That's why we're committed to creating inclusive places to work, where everyone belongs and differences are valued and celebrated.