Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

The Company

We're working with a highly successful, fast-scaling AI b2b FinTech transforming how data and workflows operate across global financial markets.

Following significant growth and Series C funding, they're now heavily investing in new products and international expansion.

The Role | Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

This is a high-impact Senior or Lead Backend Engineer position on the IC track, taking ownership of technical strategy and architecture across a complex, rapidly scaling engineering organisation.

Rather than owning a single product or feature set, you'll operate across multiple engineering teams, helping define the architecture and technical direction that underpins the company's next phase of growth.

You'll remain hands-on when it matters, but your impact will extend far beyond your own code - setting engineering standards, solving complex architectural problems and aligning teams around a clear technical vision.

You'll be working across areas including:

• Designing and evolving large-scale backend and distributed systems
• Defining technical strategy across Platform, AI, Retrieval and shared engineering services
• Designing scalable APIs and shared platform capabilities
• Leading complex, cross-team technical initiatives from design through to production
• Improving reliability, scalability, observability and developer experience
• Working closely with AI and Retrieval teams across search, RAG and data-intensive systems
• Reducing architectural complexity and establishing common engineering patterns
• Contributing hands-on to critical technical work while raising standards through design reviews and mentoring
• Using AI-assisted engineering to improve productivity and accelerate delivery

What We're Looking For | Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

• Strong experience designing and building large-scale backend systems and distributed architectures
• Excellent systems design skills, with evidence of making significant architectural decisions
• Experience leading technically complex initiatives across multiple engineering teams
• Strong backend programming experience with Python or another modern backend language
• Strong experience with AWS, Kubernetes, APIs and modern cloud infrastructure
• Comfortable influencing engineering strategy without direct authority
• Able to move between high-level technical strategy and hands-on engineering
• Strong communication skills with experience mentoring engineers and raising engineering standards
• Comfortable making pragmatic technical trade-offs in complex, scaling environments

Experience with AI-powered systems, RAG, search platforms, retrieval systems or vector databases would be particularly valuable.

Experience as a Founding Engineer / CTO, building systems from scratch in an early-stage environment, or modernising complex legacy systems would also be highly relevant.

What's On Offer | Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

• Up to £140,000 base salary + equity
• Private medical insurance
• Flexible hybrid or remote working
• 25 days' holiday + public holidays
• Professional learning & development budget
• 1-month paid sabbatical after 5 years
• Significant influence over the architecture and technical direction of a rapidly scaling engineering organisation

Senior & Lead Backend Engineer (Python) | AI FinTech, B2B | Systems Design + Technical Leadership at scale | £100-140k + Equity | London, Hybrid

This is an opportunity for a genuine Staff-level Backend / Platform Engineer who enjoys solving difficult systems problems, influencing architecture across multiple teams and remaining close enough to the code to lead by example.