Machine Learning Engineer (up to £230k)

Dex; Greater London; On-site; GBP 90,000 - 125,000; Full time

Job summary

Dex's partner company in London is seeking an experienced ML engineer to design, ship, and diagnose production ML models that directly influence user engagement and company earnings. You will contribute to the core ML infrastructure and work across training pipelines to live model serving, balancing business value with technical rigor.

The role emphasizes end-to-end ownership, from data pipeline through to deployment, with a focus on measurable impact and a fast feedback loop in a growing

Qualifications

• Hands-on production ML with end-to-end delivery.
• Experience across data pipeline, model, and live serving.
• Strong statistics background: A/B testing, regression, probability.
• Familiar with causal inference or uplift methods.
• Focus on business impact and high-leverage solutions.
• Interest in building ML infrastructure alongside the team.

Responsibilities

• Design and ship production ML models impacting engagement and earnings.
• Translate complex business problems into ML formulations.
• Build and optimize reward and payout structures balancing cost and value.
• Diagnose underperforming reward campaigns and implement solutions.
• Contribute to ML infrastructure design and implementation from training to serving.

Skills

Production ML

Full stack ML

Statistics (A/B testing)

Causal inference

ML infrastructure

Job description

This role is with one of Dex's trusted partner companies. We work closely with their teams to truly understand their culture, goals, and what they're looking for, so we can match you with the right opportunity and give you context about the role before you commit to a process.

This company runs a bootstrapped rewards platform with 80 million users, profitable since day one. The models you build here directly decide what users see and what the company earns, offering a rare, direct line from your work to significant business impact. They are one of Europe's fastest-growing companies, expanding their data and ML function in London.

You'll join a deliberately small data and ML team, owning the entire surface end-to-end. This isn't a role where you hand off models; you'll design, ship, and diagnose them, with a short feedback loop measured in weeks. You'll also help build the ML infrastructure, not just consume it, across a range of problems from reward ranking to personalization and measurement.

The work

• Design and ship production machine learning models that directly impact user engagement and company earnings.
• Translate complex mathematical business problems into concrete ML formulations.
• Build and optimize reward and payout structures, balancing user motivation with cost sustainability and advertiser value.
• Diagnose and troubleshoot underperforming reward campaigns, identifying root causes and implementing solutions.
• Contribute to the design and implementation of the core ML infrastructure, from training pipelines to live model serving.

What You Bring

• You are genuinely hands-on in production ML, having shipped models end-to-end rather than handing them off.
• You work across the full stack of a problem: data pipeline, model, and live serving.
• You have a strong grounding in statistics, including A/B testing, regression, and probability, ideally with causal inference or uplift methods.
• You are motivated as much by business impact as by technical elegance, prioritizing high-leverage solutions.
• You want to build ML infrastructure alongside your team, not just use existing systems.