Senior Backend Engineer - C#/Python - London

Oliver Bernard; Greater London; On-site; GBP 80,000 - 90,000; Full time

Benefits offered by this job

Equity

Unlimited holiday

Job summary

Oliver Bernard is helping a fast-moving AI fintech startup hire a Senior Backend Engineer in London. You’ll own backend services, APIs and infrastructure, and work directly with the founders to shape the technical roadmap.

You’ll bring 3-4+ years shipping backend systems, experience with AI tooling and LLMs, and fintech domain knowledge. This early team role offers ownership, high agency, and opportunities to impact product direction.

Qualifications

• 3–4+ years shipping and owning backend systems.
• Experience with AI tooling, LLMs or agentic workflows.
• Fintech experience is essential (payments, banking, ledgers).
• Comfortable working across the stack in a fast-paced environment.

Responsibilities

• Design, build and own core backend services, APIs and infrastructure.
• Take LLM and agentic workflows from concept into production.
• Own data models, failure modes, auditability and performance.
• Build API-first systems and infrastructure.
• Jump into React / Frontend when needed to ship a feature.
• Work directly with the founders and shape the technical roadmap.

Skills

Backend development

API design

LLMs / AI tooling

Fintech domain knowledge

Full-stack readiness

Job description

Senior Backend Engineer | AI x FinTech | London | £80k + Equity + Unlimited Holiday

Oliver Bernard have recently partnered with a fast-moving AI fintech start-up that’s building an AI-native product from the ground up. They’re now looking for a Senior Backend Engineer to join their early engineering team.

This is an opportunity to get in early, work directly with the founders and take real ownership of the technology.

What you'll own

• Design, build and own core backend services, APIs and infrastructure
• Take LLM and agentic workflows from concept into production
• Own data models, failure modes, auditability and performance
• Build API-first systems and infrastructure
• Jump into React / Frontend when needed to get a feature shipped
• Work directly with the founders and help shape the technical roadmap

What they're looking for

• 3-4+ years shipping and owning backend systems
• Experience with AI tooling, LLMs or agentic workflows
• Fintech experience is essential - payments, banking, open finance, ledgers or financial infrastructure particularly relevant
• Comfortable operating across the stack when needed
• Someone who thrives in high-agency, fast-paced environments

This is an early team hire, so you’ll have a level of ownership and influence that’s difficult to find in a larger organisation.

You’ll be close to the founders, have a direct impact on the product and get the chance to work at the intersection of AI + financial technology.

London, 3-4 days in office