Senior AI Engineer (Machine Learning/Prompt Engineer)

Benefex Limited; Southampton; Hybrid; GBP 70,000 - 90,000; Full time

Job summary

A fast-growing technology company in Southampton is looking for a Generative AI Engineer to enhance their AI capabilities across products. You will be integral in designing AI systems that improve user experience and operational efficiency, working within a dynamic team focused on innovation in the benefits solutions space.

Benefits

Flexible work setup

£/€800 annual learning budget

25 days holiday plus bank holidays

Birthday off

Healthcare cash plan

Income protection and life assurance

£50 monthly allowance for personal use

Qualifications

• Proven experience as a senior engineer in a SaaS company.
• Experience with LLMs and ML libraries.
• Ability to work collaboratively in cross-functional teams.

Responsibilities

• Design, build, and maintain AI systems and tools.
• Collaborate to identify AI opportunities across product suite.
• Develop scalable pipelines for data ingestion and model deployment.

Skills

Python

Machine Learning

Prompt Engineering

Data Pipeline

Problem Solving

Education

Bachelor's Degree in Computer Science or related field

Tools

TensorFlow

PyTorch

LangChain

Google Cloud Platform (GCP)

Job description

Who are Benifex?

We are a fast-moving technology company, and one of the most successful providers of online reward and benefits solutions in the UK. We believe that everyone deserves an exceptional experience at work, every day, and build workplace technology that makes this happen. Benifex’s mission is to build remarkable experiences that employees love. Today Benifex supports more than five million employees in over 3,000 organisations across more than 100 countries. To help us on our quest to be the best, we need brilliant people on board and that’s where you come in.

Why should you apply?

• Impact: Play a central role in shaping our AI capabilities across out products
• Tech: Work withVertex AI, AlloyDB, LangChain, GCP
• Greenfield: Join a newly formed team working on a product that is used my millions of users around the world
• Sunday Times Best Place to Work 2025 and Best Large Tech Company to Work for 2025
• Work for a profitable, fast-growing market leader in the online reward and benefits space

**Please note we are unable to offer visa sponsorship and require to people to be based in the UK or Ireland for this position**

Great benefits:

£70,000-90,000

Tech setup of your choice (MacBook Pro or equivalent, monitors, etc.)

£/€800 annual learning budget, plus two hours per week as ‘Focus Fridays’.

Flexible work – choose a working setup that works for you, our only ask is to see you once a quarter in our UK HQ and you need to be based in UK or Ireland

️ 25 days holiday plus your local bank holidays

Your birthday off

️ Two half day wellbeing days

???? Healthcare cash plan to cover the costs of day to day healthcare

Employee Assistance Plan 24/7 365 support

Income Protection (75%) and life assurance (4x salary)

Pension scheme

£50 monthly allowance to spend on whatever takes your fancy, your very own Benifex card will be topped up at the start of each month!

Role Overview

We’re seeking a skilled Generative AI Engineer to join our AI Squad and play a key role in advancing our AI capabilities across Benifex products. You’ll work at the heart of our AI initiatives, partnering with engineers, product managers, and data stakeholders to design and implement AI-powered services that enhance user experience and operational efficiency.

You will have the opportunity to make a real difference by ensuring the stability and performance of a platform used by millions. We work in a dynamic environment, where we learn and grow by tackling complex technical challenges.

Responsibilities

• Design, build, and maintain AI systems and tools using machine learning and large language models (LLMs), with a strong focus on prompt engineering and model fine-tuning.
• Collaborate with cross-functional teams to identify opportunities for AI and automation across the product suite.
• Develop scalable pipelines for data ingestion, model training, evaluation, and deployment.
• Prototype and iterate on prompt designs to maximise the relevance, coherence, and usefulness of LLM outputs.
• Work with cloud infrastructure (GCP preferred) and MLOps tools to deploy, monitor, and manage AI services.
• Contribute to the development of reusable AI components and APIs to support product and internal teams.
• Stay informed of the latest developments in machine learning and generative AI to drive continuous improvement.

What are we looking for?

Technical Proficiency:

• Proven experience operating as a senior level engineer within a product or SaaScompany
• Proven experience with Python and ML libraries such as TensorFlow or PyTorch.
• Experience working with LLMs (Gemini), prompt engineering, and reinforcement learning from human feedback (RLHF).
• Experience with LangChain for building LLM applications with RAG pipelines and agent workflows.
• Practical understanding of vector search, embeddings, and retrieval-augmented generation (RAG).
• Experience building and deploying machine learning models into production environments.
• Familiarity with MLOps tools and practices (Vertex AI).
• Understanding of data pipelines, data preparation, and feature engineering.

Bonus Points for:

• Hands-on experience with prompt tuning, fine-tuning LLMs, or adapting open-source models for specific use cases.
• Hands-on experience with AlloyDB or similar.
• Experience working in cloud environments, particularly Google Cloud Platform (GCP).

General engineering traits that we look for:

Taking ownership: A mindset of holding yourself and others accountable, someone who can be relied on in challenging situations, a bias to action.

Passion for technology: Someone who invests in their craft and self learning, a continuous improvement mindset, a focus on best practices, and someone keen to see how new tools/technology can be applied to business problems.

Open mindedness: Strong opinions loosely held, you're open to ideas, and seek feedback and input from others.

Excellent communicator: An effective communicator to techncial and non-technical audiences, able to break down complex information into simple to understand language.

Natural problem solver: someone who thrives on solving technical challenges, who has a methodical way to work through problems and offer pragmatic solutions

Even if you don't meet all of the requirements for this role, we encourage you to apply! We are looking for talented and passionate individuals who are eager to learn and grow. We also offer a variety of other roles, so please check out our careers page to see if there is something else that might be a good fit for you.

Our interview process

Benifex understand the need to have a fast and efficient process, the below will all be completed in the shortest time possible (typically 2-3 weeks)

Initial informal call with the Talent team

30 minute interview with anEngineering Manager

Technical Task

60 min interview with the Hiring Manager and 1-2 Engineers

30 min final interview with our VP of Engineering

We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, colour, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.

We are committed to creating a diverse and inclusive workplace where everyone feels welcome and respected. We believe that diversity and inclusion are essential to our success, and we are proud to be an equal opportunity employer.

We are a proud member of the Disability Confident employer scheme.

If you require any reasonable adjustments at any stage during the recruitment process, please let us know with your application.