Junior Data Scientist

Yaspa; Greater London; On-site; GBP 55,000 - 90,000; Full time

Job summary

Yaspa is seeking a data scientist to preprocess transaction data, build features, and support ML model evaluation. You will work with NLP to clean messy text fields and create ground-truth datasets, then expose insights at customer and merchant levels for product and engineering teams.

The role involves collaborating with cross-functional partners, applying statistical methods, and improving binary classification models through cross-validation and error analysis.

Qualifications

• Bachelor’s or Master’s degree in Data Science, Computer Science, Statistics, or Mathematics, or 1 year+ professional experience
• (Desirable) Demonstrated ability to design and validate features using transactional and behavioural data from financial services
• Some hands-on experience building ML models in Python
• (Desirable) Experience building and improving AI agents for specific tasks
• Working SQL skills
• (Desirable) Payment risk, fraud detection, or credit decisioning is a plus
• Solid understanding of supervised and unsupervised learning, particularly binary classification, cross-validation, and common evaluation metrics
• (Desirable) Any exposure to AWS is a bonus
• Comfortable working with tabular data
• Interest in working with product and engineering teams
• Curious, proactive, and comfortable working in ambiguity in a scaling start-up environment
• Detail-oriented and consistent, comfortable with careful, repetitive data work

Responsibilities

• Clean and prepare raw transaction data for analysis and labelling, using natural language processing (NLP) techniques to parse and normalise messy text fields such as merchant names and descriptions
• Aggregate transaction data into customer- and merchant-level views, and surface behavioural insights such as spending patterns and recurring payments that inform features and labels
• Own the creation of ground-truth datasets from transaction data: define and apply labelling standards, run quality checks, and resolve ambiguous cases. Where possible, speed up labelling with heuristics, rules, and simpler models, and measure their accuracy against manually labelled samples
• Help build and test transaction-categorisation logic, for example surfacing merchant information, applying labels, and recording confidence scores
• Use Python for data preparation, feature engineering, and model evaluation, supporting the team's machine learning (ML) work
• Help validate model outputs, mostly for binary classification tasks, using cross-validation and confusion matrices, and reviewing precision, recall, and error patterns to flag where a model underperforms
• Apply a solid understanding of statistics and hypothesis testing to spot trends and support model development
• Work closely with cross-functional teams across product, engineering, and business stakeholders to understand requirements and deliver data-driven solutions
• Enthusiasm for collaborating across disciplines, including with academic researchers and third-party partners

Skills

Python

SQL

NLP

Data analysis

Collaboration

Education

Bachelor’s or Master’s degree in Data Science/CS/Statistics/Mathematics

Tools

Python

AWS

Job description

Requirements

• Bachelor’s or Master’s degree in Data Science, Computer Science, Statistics, Mathematics, or 1 year+ professional experience
• (Desirable) Demonstrated ability to design and validate features using transactional and behavioural data from financial services
• Some hands-on experience building ML models in Python
• (Desirable) Experience building and improving AI agents for specific tasks
• Working SQL skills
• (Desirable) Payment risk, fraud detection, or credit decisioning is a plus
• Solid understanding of supervised and unsupervised learning, particularly binary classification, cross-validation, and common evaluation metrics
• (Desirable) Any exposure to AWS is a bonus
• Comfortable working with tabular data
• Interest in working with product and engineering teams
• Curious, proactive, and comfortable working in ambiguity in a scaling start-up environment
• Detail-oriented and consistent, comfortable with careful, repetitive data work

What the job involves

• Clean and prepare raw transaction data for analysis and labelling, using natural language processing (NLP) techniques to parse and normalise messy text fields such as merchant names and descriptions
• Aggregate transaction data into customer- and merchant-level views, and surface behavioural insights such as spending patterns and recurring payments that inform features and labels
• Own the creation of ground-truth datasets from transaction data: define and apply labelling standards, run quality checks, and resolve ambiguous cases. Where possible, speed up labelling with heuristics, rules, and simpler models, and measure their accuracy against manually labelled samples
• Help build and test transaction-categorisation logic, for example surfacing merchant information, applying labels, and recording confidence scores
• Use Python for data preparation, feature engineering, and model evaluation, supporting the team's machine learning (ML) work
• Help validate model outputs, mostly for binary classification tasks, using cross-validation and confusion matrices, and reviewing precision, recall, and error patterns to flag where a model underperforms
• Apply a solid understanding of statistics and hypothesis testing to spot trends and support model development
• Work closely with cross-functional teams across product, engineering, and business stakeholders to understand requirements and deliver data-driven solutions
• Enthusiasm for collaborating across disciplines, including with academic researchers and third-party partners