Machine learning engineer
Train, evaluate and maintain models for a defined task.
The outcome this role owns
A reproducible model that performs adequately on relevant unseen data and remains useful as conditions change.
Four levels of maturity
Proposed framework · Evidence-based discussion · Not a validated assessment scale
Foundation
Reproduces a baseline and explains train, validation and test splits.
Evidence to look for
A baseline with clear dataset boundaries
Pilot
Builds a repeatable experiment, checks leakage and reports errors across relevant cases.
Evidence to look for
Reproducible experiments and segment-level errors
Production
Owns a deployed model, monitors performance changes and documents retraining and rollback decisions.
Evidence to look for
Monitoring history and a tested retraining procedure
Organisational
Sets modelling standards across teams and chooses when a simpler model or different data strategy is preferable.
Evidence to look for
A model review showing a justified trade-off
A practical work sample
Give the candidate an apparently strong model result with a potential time leak. Ask them to audit the split, propose a valid baseline and explain the business cost of different errors.
Use synthetic or public data, explain the evaluation criteria in advance and allow reasonable adjustments. Discuss the reasoning as well as the finished artifact.
What to question
A single accuracy score without the test population, leakage checks or an account of costly mistakes.
Related market signal: machine learning
Machine-learning adoption describes enterprise use for data analysis. It is not a count of ML engineers, researchers or open positions.
Highest observed shares among covered markets, 2025. These are context, not recommended hiring locations.
Eurostat source and definitions ↗
Salary context
Check source role titles carefully. Broad categories and adjacent roles are labelled.
Explore related salary evidence ↗Framework sources
This guide is an original synthesis drawing on the sources below. The sources do not publish or endorse these role levels.