Senior Software Engineer - Data & Infrastructure

Harnham - Data & Analytics Recruitment; London; On-site; GBP 125,000 - 150,000; Part time

Job summary

A technology-focused recruitment firm is looking for a Software Engineer to join their team in London on a 6-month contract. The role involves building backend services and APIs for data preparation and model training, with a focus on machine learning workflows. Ideal candidates will have strong skills in Python, Java, or Scala and experience with ML tools such as MLflow and Docker. This position offers a pay of £450-£550 per day, outside IR35.

Qualifications

• Strong experience in Python, Java, or Scala for backend development.
• Solid understanding of data processing and engineering workflows.
• Experience building APIs or services to support data or ML applications.

Responsibilities

• Building backend services and APIs to support data preparation and model training workflows.
• Collaborating with Data Scientists and Engineers to streamline LLM/ML experimentation and deployment.
• Implementing tools for dataset validation, monitoring, and reproducibility.

Skills

Python

Java

Scala

Problem-solving

Tools

MLflow

Airflow

Docker

Job description

SOFTWARE ENGINEER - DATA & ML INFRASTRUCTURE
6-MONTH CONTRACT

£450-£550 PER DAY (OUTSIDE IR35)

This role offers a great opportunity for a Software Engineer to join a high-performing data function building out infrastructure for cutting-edge ML and LLM use cases. You'll work closely with Data Engineers and Data Scientists to design clean, production-ready systems that support model training, fine-tuning, and deployment. The environment values autonomy, quality, and technical curiosity, with the freedom to shape best practices in a fast-scaling ML context.
THE COMPANY
This is a tech-forward business investing heavily in AI and machine learning, with a focus on scalable systems and real-world impact. With a modern data platform already in place, they're now scaling up their ML/LLM capabilities and need a strong software engineer to help operationalise model development workflows. You'll be joining a collaborative, cross-functional team working at pace to solve complex technical challenges.
THE ROLE
You'll sit at the intersection of data and machine learning, building services and tooling that bridge raw data with production-grade ML pipelines. From preparing high-quality training data to designing APIs for model inference, you'll help enable the full lifecycle of ML and LLM deployment.

Your responsibilities will include:

• Building backend services and APIs to support data preparation and model training workflows.
  
• Collaborating with Data Scientists and Engineers to streamline LLM/ML experimentation and deployment.
  
• Implementing tools for dataset validation, monitoring, and reproducibility.
  
• Supporting the development of real-time and batch inference pipelines.
  
• Contributing to the scalability, efficiency, and reliability of ML infrastructure.
  

KEY SKILLS AND REQUIREMENTS

• Strong experience in Python, Java, or Scala for backend development.
  
• Solid understanding of data processing and engineering workflows.
  
• Experience building APIs or services to support data or ML applications.
  
• Familiarity with ML model lifecycle and tooling (e.g. MLflow, Airflow, Docker).
  
• Strong problem-solving skills and the ability to work autonomously in a dynamic environment.
  

DESIRABLE SKILLS

• Experience supporting LLM training or retrieval-augmented generation (RAG).
  
• Familiarity with feature stores, vector databases, or embedding pipelines.
  
• Understanding of data quality, lineage, and governance best practices.
  
• Exposure to cloud platforms (AWS, Azure, or GCP) and distributed compute environments.