Senior Full Stack Engineer

Reporting to: Engineering Manager

Office Environment: Hybrid (minimum two days per week)

Type: Full time, permanent

Join Our Mission

Skip the queue. Shape the future. See real impact.

At QuantSpark, we’re transforming how data and AI serve society. We combine the analytical discipline of strategy consulting with the pace and ownership of a scale-up. That means you’ll work directly on the problems that matter most—whether combating economic crime, modernising government services, or accelerating commercial growth for FTSE 100 companies.

Here, you’ll compress 5–10 years of traditional career progression into 2–3 years. From day one, you’ll lead end-to-end projects, access leadership directly (including the CEO), and build cross-industry expertise that usually takes a decade to gain.

We don’t just develop—we build, own, and scale solutions that shape the organisations we work with and have meaningful societal impact.

Our Client Portfolio

We partner with forward-thinking organisations across sectors:

• Private Equity & Financial Services: Portfolio analytics, AI-powered value creation, and risk management tools for global investment and wealth firms.
• Retail & Consumer: Pricing optimisation, inventory efficiency, and personalised engagement for major UK retailers and brands.
• Asset Management: Advanced investment platforms and automated risk management for asset managers.
• Public Sector: Trusted by multiple UK government departments for fraud analytics, predictive maintenance, and supply chain optimisation.
• SaaS & Manufacturing: Sector-spanning technology transformation for SaaS innovators and manufacturers.

The Role

As a Senior Developer, you’ll design, build, and scale robust, impactful web applications using both backend and frontend technologies. In this role, you’ll:

• Drive the architecture, design, and delivery of scalable, secure, and maintainable software solutions for commercial clients across multiple sectors.
• Guide and mentor junior developers through hands-on leadership, code reviews, and knowledge-sharing.
• Write, review, and own high-quality code primarily in Python (using frameworks like Flask, FastAPI, or Django) and JavaScript/TypeScript (preferably React).
• Develop and maintain RESTful APIs and modern user interfaces, ensuring an excellent user experience and technical excellence.
• Work directly with clients providing technical expertise and guidance
• Use AI coding agents (e.g., GitHub Copilot, Cursor, Claude/ChatGPT-based workflows, etc.) to accelerate delivery while ensuring correctness and security.
• Work with cross-functional teams to gather requirements, design solutions, and deliver features that make a meaningful impact.
• Exposure to system design and technical strategy in a cloud environment, containerisation and database systems.
• Collaborate closely with Data Engineers on data pipelines and large-scale data processing.
• Champion best practices in software engineering, TDD/unit testing, and documentation.

AI Engineering & coding-agent expectations (required)

• Hands-on experience using AI coding agents in day-to-day development (prompting, iterative refinement, reviewing generated code, and validating outputs).
• Practical understanding of core AI Engineering concepts, such as:
• LLM fundamentals and limitations (hallucinations, context limits, evaluation mindset)
• Prompting patterns and tool use (function calling/tool invocation concepts)

You Should Hit the Apply Button If…

• You’re an experienced full-stack engineer (5+ years), with at least 1 year in a senior or lead role, regularly mentoring others.
• You have a track record in designing and delivering enterprise-grade web applications and APIs.
• You’re deeply knowledgeable in Python backend frameworks and modern frontend frameworks (React/TypeScript), and comfortable across the full product lifecycle.
• You enjoy solving complex technical problems, delivering elegant code, and driving architectural decisions.
• You’re proactive, accountable, and collaborate well in fast-paced, cross-functional teams.
• You’re excited by autonomy, and the chance to shape both team standards and technical direction.

I Want to Work for a Company That…

• Accelerates my growth by giving me tech ownership and autonomy from day one
• Lets me see my work and high-value impact within months
• Provides direct exposure to executives, not layers of hierarchy
• Values diversity of thought, background, and approach

I’m Looking to Work With…

• A team of technical entrepreneurs who think differently and thrive on technical challenge
• Colleagues who share openly, challenge constructively, and grow together
• Clients who are ambitious enough to reimagine how data and technology transform their organisations

In 3–5 Years I Want to Be…

• Leading end-to-end technical programmes where my architectural and product designs set benchmarks

Perks & Benefits

• £6,000 annual training&conference budget to stay at the cutting edge
• Up to 6% matched pension for long-term financial security
• Comprehensive private healthcare via Vitality
• EMI share options scheme—own a piece of the growth you help create
• Work from anywhere in the world for up to 1 month/year
• 25 days holiday + buy/sell up to 5 additional days
• Cycle-to-work scheme for sustainable commuting
• Central London office stocked with refreshments, socials, and vibrant atmosphere
• Exclusive discounts on retail, travel, tech&fitness memberships
• Access to cutting-edge tools, platforms, and regular tech talks&innovation time

Equal Opportunities

We're building a team that benefits from different perspectives, experiences, and ways of thinking. We know that great talent comes from all backgrounds, and we encourage applications from everyone who meets the role requirements, regardless of age, disability, gender identity, race, religion, sexuality, or any other characteristic. If you're unsure whether you're a perfect fit but believe you can do the job well, we'd still like to hear from you. We hire based on your skills, potential, and ability to contribute to our team, and we're committed to a fair and objective selection process for all candidates.