Mid-Level Full Stack Developer

CompanyQuantSpark

LocationLondon, England, United Kingdom

Posted At3/5/2026

UK Visa Sponsorship Analytics

Occupation Type

Programmers and software development professionals

Occupation Code Skill LevelHigher Skilled

Sponsorship Salary Threshold

£54,700 (£28.05 per hour)

Occupation rate applies

Above analytics are generated algorithmically based on job titles and may not always be the same as the company's job classification. You can also check detailed occupation eligibility, and salary criteria on our UK Visa Eligible Occupations & Salary Thresholds page.

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Description

Title: Mid-Level Full Stack Developer
Reports to: Engineering Manager
Location: London (Hybrid, 2 days office based per week)
Type: Full-Time, Permanent

Candidates must be eligible for Security Clearance

Join Our Mission

At QuantSpark, we're transforming how data and AI serve society. Our team partners with forward-thinking organisations across multiple sectors to harness the power of analytics and artificial intelligence, creating meaningful impact that extends far beyond financial outcomes.

Our impressive client portfolio:

Private Equity & Financial Services: AI-powered analytics and risk tools for top investment firms.
Retail & Consumer: Inventory optimisation and personalised customer experience solution.

Asset Management: Investment decision support and automated risk management systems.

Public Sector: Predictive maintenance, supply chain optimisation, and process automation.

SaaS, Manufacturing & More: Diverse industry challenges requiring innovative analytics.

Internal SaaS Products

In addition to serving our consulting clients, we also develop proprietary SaaS products tailored for B2B applications across a range of industries.

What you’ll do

Build and maintain full-stack web features using Python backend frameworks (e.g., FastAPI/Django/Flask) and React (JavaScript/TypeScript).
Design, develop, and document RESTful APIs; integrate them with responsive, accessible UIs.
Work with product and design to turn requirements into well-scoped technical solutions.

Write clean, testable, maintainable code and contribute to code reviews and engineering standards.

Use AI coding agents (e.g., GitHub Copilot, Cursor, Claude/ChatGPT-based workflows, etc.) to accelerate delivery while ensuring correctness and security.

Help improve development workflows (DX), including tooling, CI/CD, linting, testing, and observability where relevant.

Collaborate effectively across a small team, owning features end-to-end.

Required qualifications

1–3 years of progressive full-stack engineering experience (commercial/professional).
1+ year of commercial experience with a Python backend framework (FastAPI/Django/Flask) and JavaScript or TypeScript (ideally React).
Experience building and consuming

REST APIs and developing modern web UIs.

Strong understanding of Git and common branching / PR workflows.

Familiarity with at least one database system: PostgreSQL, MySQL, MongoDB (schema design and basic query performance awareness).

Demonstrated ability to solve problems independently and deliver reliable features.

Strong communication skills—comfortable collaborating async and in teams.

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)

Basics of RAG (retrieval-augmented generation) and embeddings at a conceptual level

Safety/privacy awareness when using AI tools (secrets, PII, licensing concerns)

Ability to integrate AI assistance into an engineering workflow while maintaining code quality (tests, reviews, reproducibility).

Nice to have

Experience with async Python, background jobs/queues (Celery/RQ), and API auth (JWT/OAuth).
Frontend state management and UI patterns (React Query, Redux, component libraries).
Docker, CI/CD, cloud fundamentals (AWS/GCP/Azure), and basic observability (logs/metrics).
Exposure to integrating LLM features into products (e.g., OpenAI/Anthropic APIs), basic evaluation, and prompt/version management.

Why You'll Love QuantSpark

Work That Matters: Lead high-impact analytics projects across diverse sectors—from building predictive models that help private equity firms identify value creation opportunities to creating inventory optimisation algorithms for household-name retailers. Tackle Exciting Challenges: Design and implement technically sophisticated solutions such as real-time analytics platforms for FTSE 100 companies, automated risk assessment systems for asset managers, and predictive maintenance pipelines for government departments.

Shape Technical Standards: As a growing consultancy, you'll help define our analytics engineering practices, tooling choices, and data architecture patterns that will serve as the foundation for our continued growth.

Work Alongside Brilliant Minds: Collaborate with exceptionally talented colleagues who bring diverse expertise from leading universities, top tech companies, and varied industry backgrounds—all united by intellectual curiosity and a drive to solve meaningful problems.

Innovate with Purpose: Explore cutting-edge approaches to analytics engineering, from modern data stack implementations to GenAI tooling, ensuring QuantSpark stays at the forefront of the industry.

Benefits

£6,000 annual training & conference budget to keep you at the cutting edge of analytics engineering.
Up to 6% matched pension for your long-term security.
Comprehensive private healthcare through Vitality.
Work from anywhere in the world for up to one month per year.

25 days holiday plus flexibility to buy/sell up to 5 additional days.

Sustainable commuting support through our cycle to work scheme.

Engaging Central London office environment with quality refreshments, regular team socials, and a vibrant atmosphere.

Exclusive discounts on retail, travel, technology, and fitness memberships.

Access to cutting-edge analytics tools and platforms.

Regular tech talks, knowledge sharing sessions, and 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.