Principal Developer at The Granite Group in Liverpool, England, GB

We’re building a new data-driven product line, and we’re looking for a Principal Developer to lead the engineering behind it.

This is a greenfield opportunity at the heart of a new business initiative built on telematics. Connected vehicles generate a continuous stream of telemetry: millions of data points describing how, when and where people drive. Your job is to turn that raw, high-volume data into reliable platforms, real-time insight and products that change how we understand risk and serve our customers.

Job Title: Principal Developer
Location: Liverpool City Centre HQ / Hybrid (3 days in office)
Salary: Up to £100,000 depending on experience

As the Principal Developer you’ll lead a mixed team of data engineers and backend developers, and work hand in hand with our data scientists to take models from notebook to production. You’ll make the foundational decisions on how data is ingested, stored, processed and served, and you’ll set the engineering culture for a team that moves fast and builds things that scale.

We operate with the pace and energy of a scale-up, backed by the stability and customer base of an established business. Priorities shift as we learn, and we move quickly from idea to production. If you thrive on ambiguity, enjoy hard data problems and want to see your work powering live products within weeks, you’ll feel at home here.
Above all, we’re looking for an AI-native engineer. You’ll work agentically by default, using AI coding agents to design pipelines, write and test code, explore data and accelerate delivery, and you’ll help your team do the same safely and well. You’ll stay hands-on, and work closely with the Architecture Team to make sure what you build forms a durable foundation for our long-term data strategy.

You’ll define how we handle telemetry at scale. The architecture you design will determine how quickly we can launch new data products, how accurately our data science teams can model behaviour and risk, and how well the platform copes as data volumes grow. The patterns you establish for data engineering and agentic development will become the blueprint for data work across the business.

What you’ll be doing:
• Lead a mixed team of data engineers and backend developers to design, build and launch a new telemetry-driven platform from the ground up
• Architect high-throughput ingestion and processing pipelines for large volumes of streaming and batch telemetry data
• Design data models and storage strategies that balance cost, performance and query patterns across hot, warm and cold data
• Integrate data from multiple third-party telematics providers, normalising disparate formats into a consistent, trusted data model
• Lead the migration of data from legacy stores into modern, cloud-native platforms with minimal disruption
• Partner closely with data scientists to productionise models, build feature pipelines and create fast feedback loops between experimentation and live products
• Build event-driven microservices in .NET and Azure that expose data and insight to products and customers
• Champion data quality, lineage, observability and governance, so the business can trust and act on its data
• Drive agentic engineering practices across the team, using AI coding agents (such as Claude Code, GitHub Copilot and Cursor) to plan, build, test, review and document pipelines and services
• Set clear guardrails for AI-assisted development covering data security, privacy, quality and maintainability, including the safe use of tools like MCP servers against sensitive data
• Move quickly from idea to MVP to production, iterating based on real data and customer feedback
• Manage, mentor and grow the engineers in your team, helping them become confident AI-native engineers
• Act as a technical authority across engineering, influencing standards, architecture decisions and how the wider organisation adopts agentic engineering
• Set standards for Python across the team, covering code quality, testing, packaging and deployment, so data science and data engineering code is as production-ready as our .NET services
• Make pragmatic choices about when to use Python and when to use .NET, designing clean integration points between Python-based data and ML workloads and our event-driven microservices
Our Tech Stack
• Backend: C#, .NET 10.0, Redis, MongoDB, SQL Server, MassTransit, Mediator
• Data: Azure Blob and Table Storage, Amazon S3, streaming and batch processing, time-series and analytical data stores
• Messaging and Integration: Azure Service Bus, RabbitMQ, event-driven patterns
• Infrastructure: Azure, AWS, Docker, Kubernetes (AKS), Nginx
• Architecture: Microservices, Event-driven patterns, Clean Architecture
• Observability and Monitoring: Grafana, Loki, Sentry, PostHog
• AI and Agentic Tooling: AI coding agents, LLM-assisted workflows, MCP integrations
• Tooling and Practices: Git, CI/CD pipelines, Agile and lean delivery
• Data and Python: Python for data processing, pipelines and model serving, alongside the libraries and tooling used by our data science team (such as pandas, Polars and PySpark)

What we’re looking for:
• Significant experience as a senior or principal engineer leading the design and delivery of data-intensive systems
• A track record of building platforms that handle large data volumes, ideally including streaming, IoT, telemetry or time-series data
• Strong backend engineering skills in .NET and Azure, with a solid grasp of distributed systems and event-driven architecture
• Deep knowledge of data engineering: ingestion, pipelines, data modelling, partitioning, storage formats and performance tuning at scale
• Experience working closely with data scientists, and an understanding of what it takes to get models and features into production reliably
• Experience leading and mentoring mixed teams of engineers across data and software disciplines
• Real, hands-on experience using AI coding agents in your day-to-day work, with opinions on what works, what doesn’t and why
• An understanding of how to get reliable output from AI, including context engineering, task decomposition, review and verification
• Experience building products from scratch or in early-stage, fast-moving environments such as a startup, scale-up or new venture
• Comfortable making pragmatic decisions with incomplete information, and knowing when to move fast and when to invest in foundations
• A strong appreciation of data security, privacy and governance, particularly when handling sensitive customer data
• Product-focused and commercially aware, with a clear sense of how data creates value for customers and the business
• Excellent communicator who can explain complex data and architecture decisions to technical and non-technical audiences alike
• Curious, proactive and always experimenting with better ways to build, measure and deliver
Nice to have: experience with telematics, connected vehicles or insurance data; multi-cloud data platforms; MLOps practices; Python for working alongside data science teams.

Why Join Us
• Build a new telemetry-driven product line from a blank slate, with real ownership over its technical direction
• Solve genuinely hard problems with large, real-world data sets
• Work at the frontier of agentic engineering, with the backing to experiment and the tools to do it properly
• Scale-up pace and autonomy, with the security of an established business behind you
• Work alongside data scientists, engineers and product professionals who care deeply about what they build
• Real influence on engineering standards, data strategy and how the wider organisation adopts AI
• Clear growth paths into distinguished engineering, data architecture or engineering leadership roles
• A supportive, transparent culture where craftsmanship, curiosity and learning are celebrated
• Regular opportunities for professional development, conferences and innovation time

Team and Culture

You’ll join a small, high-energy team where data engineers, backend developers and data scientists work side by side to turn raw telemetry into products customers rely on. We believe in ownership, openness and trust. Our teams have the autonomy to make decisions, experiment and learn fast, and we’re just as happy to share a failed experiment as a successful one.

We work together in our Liverpool HQ three days a week because when you’re building something new with complex data, quick conversations, whiteboard sessions and fast feedback make all the difference.

You’ll thrive here if you love data at scale, are excited by AI and are energised by pace and ambiguity.

Grow with Acorn
At Acorn Insurance, we’re proud of our Liverpool roots — and even prouder of how far we’ve come. As part of the Acorn Group, we bring over 40 years of specialist insurance expertise to the table. From humble beginnings, we’ve grown into a national leader, now employing 1,700+ people across the UK and reached a milestone £750 million in total value of insurance policies written in 2024.
We’re growing fast, with new opportunities emerging every week. That growth is largely due to the values we share:
• • We run through walls for our customers and each other
• • We challenge the status quo
• • We succeed when we help those around us succeed
• • We decide quickly when the smart thing to do is use our judgement
Benefits:
• • A maximum of 35 days’ holiday (depending on role and tenure) including bank holidays, with additional buy/sell options
• • 24/7 mental health support & free counselling available
• ☝ Grow with us: Through career fairs, leadership programs, and learning on the go!
• • Flexible benefits, including early access to salary via our internal platform
• • Hybrid working options to support work-life balance and individual needs
• • Recognition awards, social events & more
Our Commitment to our colleague’s:
These aren’t just words — they’re the principles we live by. And we’re proud to back them up with real action, earning recognition and accreditation from leading organisations that share our commitment to people and growth:
• • Mindful Employer – championing mental health and wellbeing
• ♿ Disability Confident Level 1 & 2 – creating accessible, inclusive opportunities
• • Menopause Friendly accredited – supporting every stage of life
• •️ Armed Forces Covenant signatory – honouring those who serve
• •️ Armed Forces Defence employer recognition scheme - Supporting those who serve
• • Great Places to Work 2024/25 – fostering an engaging and positive workplace culture
• • Best Place to Work for Development – proud to be investing in people’s future
• •‍• Best Place to Work for Women – breaking down barriers to women's career progression
If you’re looking for a company with a strong culture, real career progression, and a people-first approach — all rooted in the heart of Liverpool — Grow with Acorn.
A Few Things to Know Before You Apply
We’re really excited that you’re considering joining Acorn! To help everything go smoothly, here are a couple of things to keep in mind:
If your application is successful, we will commence relevant employment checks prior to you commencing employment with us. These will include a standard criminal record check and an insolvency register check.

• Visa Requirements
Because our training is quite comprehensive, we can only consider applicants who have at least one year remaining on their Graduate or Post-Study Work visa. At the moment, we’re not able to offer visa sponsorship.
• We’re Here to Support You
We’re committed to creating an inclusive, supportive workplace where everyone can flourish. If you need any adjustments during the recruitment process—or once you’re part of the team—just let us know. Whether it’s flexible hours, adapted equipment, or a bit of extra support, we’ll work with you to make sure you can do your best work.

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