Junior Machine Learning Engineer

Trainline plc; Greater London; Hybrid; GBP 40,000 - 66,000; Full time

Benefits offered by this job

Private healthcare & dental insurance

Generous work from abroad policy

2-for-1 share purchase plans

EV Scheme to reduce carbon emissions

Extra festive time off

Family-friendly benefits

Job summary

Trainline plc is seeking a Junior Machine Learning Engineer to join a fast‑moving AI/ML platform in a hybrid London environment. You will collaborate with data scientists, software engineers and product managers to solve complex travel optimization problems using cutting-edge algorithms.

The role focuses on delivering production-ready ML solutions, owning end‑to‑end workflows from data exploration to deployment, and contributing to the ML community with a strong emphasis on learning and growth.

Qualifications

• Advanced degree in CS, Math or similar quantitative field.
• Proficiency in Python and open-source data libraries.
• Experience deploying ML models to production.
• Knowledge of predictive modeling, classification, regression or recommender systems.
• Experience with Spark.
• Familiarity with DevOps tools (Docker, Terraform) and ML Ops workflows.

Responsibilities

• Work in cross-functional teams with data scientists, software, data and product managers.
• Design and deliver machine learning models at scale delivering measurable business impact.
• Own end-to-end ML delivery lifecycle: data exploration, feature engineering, model selection/tuning, evaluation, deployments and maintenance.
• Collaborate with MLE team and stakeholders to design data-driven products using Trainline datasets.
• Create tools/frameworks to accelerate ML product delivery and improve workflows.
• Participate in the AI/ML community and foster a culture of learning and experimentation.

Skills

Advanced degree in CS/Math

Python proficiency

ML model productionising

Predictive modeling

Spark

Docker & Terraform

CI/CD

Feature engineering

Statistics

Communication

Education

Advanced degree in Computer Science, Mathematics or similar

Tools

Docker

Terraform

MLFlow

Spark

AWS EMR/ECS

Airflow

Job description

About us

At Trainline, our purpose is to empower greener travel choices, connecting people and places. 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

We’re Europe’s leading independent rail platform, helping millions of travellers find and book the best-value rail and coach journeys across our app, website and partner channels.

Our job is to make the green travel choice the best choice. By building a better train travel experience, we help more people choose rail - creating a positive impact for customers, our business and the planet.

We’re a team of more than 1,000 Trainliners from over 50 nationalities, working across London, Paris, Barcelona, Milan, Edinburgh and Madrid. Now is a brilliant time to join us and help shape the future of travel.

Introducing Machine Learning and AI at Trainline

Machine learning is at the heart of Trainline's mission to help millions of people make sustainable travel choices every day. Our ML models power critical aspects of our platform, including:

• Advanced search and recommendations capabilities across our mobile and web applications
• Pricing and routing optimisations to find the best fares for customers
• Personalised user experiences enhanced by Reinforced Learning Agents & Generative AI
• Data-driven digital marketing systems
• AI agents improving customer support

Our machine learning teams own the complete delivery lifecycle from ideation to production. We work closely with stakeholders across the business to expand the understanding and impact of machine learning and AI throughout Trainline.

The Role:

We are looking for a Junior Machine Learning Engineer to join our team help shape the future of train travel. You will be part of a highly innovative AI and ML platform working alongside engineers, scientists and product managers to tackle complex challenges by combining Trainline’s rich datasets with cutting edge algorithms. What unites our team is an expertise in the field, a love of what we do and the desire to create impactful solutions to support Trainline’s goals of encouraging sustainable travel.

As a part of Trainline you will be joining an environment where learning and development is top priority. You will have the opportunity to work with fellow ML enthusiasts on large-scale production systems, delivering highly impactful products that make a difference to our millions of users.

As a Junior Machine Learning Engineer at Trainline you will...

• Work in cross-functional teams combining data scientists, software, data and machine learning engineers, and product managers
• Design and deliver machine learning models at scale that drive measurable impact for our business
• Own the full end to end machine learning delivery lifecycle including data exploration, feature engineering, model selection and tuning, offline and online evaluation, deployments and maintenance
• Work with MLE Team and Stakeholders to help design and deliver data driven products using Trainline's extensive datasets and modern machine learning techniques
• Create the tools, frameworks and libraries that enables the acceleration of our ML products delivery and improve our workflows
• Take an active part in our AI and ML community and 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 similar quantitative discipline
• Are proficient with Python, including open-source data libraries (e Pandas, Numpy, Scikit learn etc.)
• Have experience productionising machine learning models
• Are an expert in one of predictive modeling, classification, regression, optimisation or recommendation systems
• Have experience with Spark
• Have knowledge of DevOps technologies such as Docker and Terraform and ML Ops practices and platforms like ML Flow
• Have experience with agile delivery methodologies and CI/CD processes and tools
• Have a broad of understanding of data extraction, data manipulation and feature engineering techniques
• Are familiar with statistical methodologies.
• Have good communication skills

Nice to have

• Understanding and/or hands-on experience of Reinforcement Learning theories, frameworks, and algorithms
• Experience with cloud infrastructure
• Experience with Large Language Models (fine tuning, RAG, agents)
• Experience with graph technology and/or algorithms, understanding of NLP algorithms

Our technology stack

• Python and associated ML/DS libraries (scikit-learn, NumPy, LightGBM, Pandas, TensorFlow, etc...)
• PySpark
• AWS cloud infrastructure: EMR, ECS, Athena, etc.
• MLOp/DevOps: Terraform, Docker, Airflow, MLFlow, NewRelic

The interview process

• Recruiter Call (30 minutes)
• Meeting a Machine Learning Manager(30 minutes)
• Technical Interview with 2 x Engineers (90 mins)
• Final Interview with the Head of (30-45 mins)

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.

Interested in finding out more about what it's like to work at Trainline? Why not check us out on LinkedIn, Instagram and Glassdoor!