Senior Full Stack Engineer - Fintech SaaS Scale-up)

London Bridge | Hybrid (2-3 days onsite) | Competitive Salary + Equity | High-Impact Role

Candidates must have the right to work in the UK as we are unable to provide visa sponsorship at this time.

As this role requires 2-3 days per week in our London Bridge office, candidates should be able to reliably commute to London Bridge.

About us

We are an early-stage B2B SaaS company. We are building a platform that blends human expertise with modern AI tooling to transform how financial services are delivered. Our product is in advanced beta and used daily by advisers. We are preparing to scale to paying customers. We handle sensitive financial and personal data. Trust, reliability and stability matter as much as speed of iteration.

The role

We are looking for a senior, hands-on Full-Stack Engineer to join our small, highly experienced engineering team. You will work across the entire product, from Python services and APIs to React and TypeScript UI components. You will help deliver features end-to-end while raising technical standards across the codebase.

This role suits someone who enjoys taking ownership and who cares deeply about engineering quality. You will help shape good engineering practices in a small but rapidly scaling environment. You will collaborate closely with Product and the other engineers. You will contribute to architectural decisions and ensure the platform remains robust, secure and ready for scale. Your influence can grow as the company grows.

What you will do

Build across the stack

• Deliver features end-to-end across Python backend and React and TypeScript frontend.
• Write clean, maintainable and well-tested code with clear API contracts.
• Build UI components and data-driven front-end features with strong TypeScript foundations.

Strengthen engineering standards

• Improve automated testing coverage across frontend and backend.
• Ensure CI and CD pipelines and quality gates support safe and frequent releases.
• Contribute to coding standards, documentation and review practices that lift the whole team.

Shape architecture and technical direction

• Participate in decisions around performance, scalability, tenancy and cost control.
• Contribute to a roadmap that may include evaluating alternative technologies. For example, Rust for performance-critical components.
• Apply security-by-design principles across authentication, authorisation, data handling and audit logging.

Help build a resilient and scalable platform

• Contribute to operational practices. For example, feature flags, safe rollbacks, incident handling, run-books, logging and monitoring.
• Improve performance across the stack. For example, SQL queries, React rendering and API throughput.
• Work closely with Product to scope work, plan release,s and make pragmatic build-versus-buy decisions.

What we are looking for

Experience

• Ten years or more of building and shipping production web applications.
• Strong full-stack capability with both backend and frontend experience.

Hard skills

• Python proficiency with any framework. FastAPI or Django are welcome.
• TypeScript expertise and strong React experience.
• Solid SQL experience. PostgreSQL is preferred but any advanced SQL background is welcome.
• Strong automated testing habits for unit, integration and end-to-end tests.
• Familiarity with GitHub workflows, CI and CD and standard developer tooling.
• Experience working in small teams and taking ownership of full product areas.

Mindset

• A self-starter mentality. You take ownership and enjoy solving complex technical challenges.
• Passion for creating high-quality, maintainable solutions that scale.
• Enthusiasm for working in a client-led environment where user feedback influences development.
• A collaborative approach. You thrive in cross-functional teams while working autonomously.
• High personal engineering standards. You lead by example rather than authority.

Nice to have

• Experience with Redis and Celery.
• Experience scaling multi-tenant SaaS applications.
• Experience with cloud platforms. (AWS, Google Cloud or Azure).
• Knowledge of containerisation (Docker or Kubernetes)
• Familiarity with SOC 2 readiness and security best practices.
• Experience with observability and monitoring.
• Background in fintech, lending or other regulated-data environments.
• Experience or interest in Rust or Go for performance-critical components.
• Experience designing or maintaining complex front-end state and data flows.

Why join us

• Build a product with real impact in a sector full of inefficiencies.
• Work in a small, senior team where your decisions matter.
• Help shape engineering culture and standards from the ground up.
• Hybrid working environment with autonomy and trust.
• Full private medical cover and EMI options with strong long-term upside.
• Use the latest technologies and modern AI models as part of the core product.
• Access to a full modern AI engineering stack to accelerate development and experimentation.



Our Values

We prioritise understanding our users' needs by engaging directly with them to build solutions grounded in real-world insights. Our client-led development approach ensures we're solving genuine problems, not just building features.

More heads are better than one 

We champion open communication, diverse perspectives, and collaborative problem-solving. We believe the best solutions emerge when we combine our different strengths and experiences.

Be the river, not the rock.

Adaptability drives impact and growth. We welcome new ideas, challenges, and opportunities to innovate and continuously improve. Like a river, we find ways forward while staying true to our course.

Quality today, better tomorrow

We build strong foundations that power rapid iterations to deliver ever-greater customer value. We balance pragmatism with excellence, knowing that perfection is the enemy of progress.

Interview Process

• Initial screening call with the Head of Engineering
• Technical interview
• Product interview
• Final interview

We are a team of builders, creators, and fintech enthusiasts crafting the next big thing in finance. Join us to build something amazing! We value attention to detail and creative problem-solving. A well-placed mention of the fruit that tops a Hawaiian pizza in your answer to 'What interests you about joining QDEX?' will ensure your application stands out.