Detect fraud in milliseconds, at the moment a transaction happens, without blocking legitimate customers.

Machine Learning Engineer - Spain
Madrid or Barcelona, Spain · Permanent · Hybrid

What you'd actually work on

Building and maintaining fraud detection and risk-scoring models used on live transactions

Developing features from transactional, behavioural, account, and device data

Training and evaluating models against new and evolving fraud patterns

Deploying models into low-latency production systems

Reducing false positives while maintaining effective fraud detection rates

Working with risk specialists to translate fraud scenarios and business rules into model features

Designing feedback loops using confirmed fraud cases, manual reviews, and transaction outcomes

Monitoring model performance, feature quality, drift, latency, and prediction distributions

Investigating model degradation and changes in customer or fraud behaviour

Improving model deployment, versioning, retraining, and rollback processes

Documenting model behaviour and decisions for engineers,



risk teams, and auditors

Contributing to code reviews, automated testing, CI/CD, and ML engineering standards

Where it gets technically interesting

Real-time inference under strict latency constraints, with decisions required before transactions are completed

Highly imbalanced datasets where confirmed fraud represents only a small proportion of all transactions

Fraud patterns that change deliberately in response to existing detection methods

Managing delayed or incomplete labels when transaction outcomes are not immediately known

Balancing fraud detection rates against the commercial and customer impact of false positives

Identifying drift in models and features before it results in significant financial losses

Combining machine learning outputs with business rules and manual risk controls

Meeting explainability and traceability requirements for decisions that may need to be reviewed late

📌 Machine Learning Engineer (Madrid)
🏢 The French Sourcer
📍 Madrid