Senior Backend Engineer: Core Banking & Distributed Systems

Onmo; Greater London; On-site; GBP 100,000 - 180,000; Full time

Job summary

Onmo is looking for a senior backend or full-stack engineer to help build and operate our core banking capabilities in London. You will design, implement and run money movement, interest calculation and statement generation within distributed, event-driven systems.

You’ll own foundational services, contribute to architecture decisions with the tech lead, and mentor engineers across the function while shipping reliable, well-documented code in a fast-paced fintech environment.

Qualifications

• Proven experience designing and running distributed systems in production.
• Strong Node.js/TypeScript and AWS expertise across serverless and containerised workloads.
• Infrastructure as code with Terraform; CI/CD as a habit.
• Track record of raising engineering standards through reviews, patterns, tooling or mentoring.
• Write clean, tested, maintainable code and improve system understandability.

Responsibilities

• Design, build and run core banking capabilities that are accurate, monitored and dependable.
• Build new core systems and migrate off vendors safely with parallel runs and clean cutovers.
• Own and evolve shared services, modernising patterns and improving reliability.
• Set patterns through RFCs and pave paths with libraries and guides.
• Review colleagues' contributions to core-owned services to keep high standards.
• Write tested, correct, documented code and mentor engineers.
• Shape technical direction with the tech lead on architecture and build-versus-buy decisions.
• Make systems self-serve so other teams can ship on them independently.

Skills

Correctness and reliability

Distributed, event-driven design

Documentation and knowledge sharing

Clear stakeholder communication

Startup pragmatism

Ownership of foundational systems

Ability to operate under ambiguity

Tools

Node.js/TypeScript

AWS (serverless & containers)

Terraform

CI/CD practices

Job description

Onmo is looking for a senior backend or full-stack engineer to help build and operate our core banking capabilities in London. You will design, implement and run money movement, interest calculation and statement generation within distributed, event-driven systems.

You’ll own foundational services, contribute to architecture decisions with the tech lead, and mentor engineers across the function while shipping reliable, well-documented code in a fast-paced fintech environment.