Principal Engineer

Posted: 2026-01-05

•Are you curious, excited by experimentation, and always looking for a better way of doing things? •Do you want to keep learning and developing whilst getting hands-on experience working in the payments space? •Do you want to have the opportunity to apply technology to transform the way we operate at scale.

If so, we would love to hear from you! We are looking to hire ambitious, and value-adding talent to join Modulr, the fastest growing payments business in the UK and Europe. The Principal Engineer is a hands-on individual contributor role with broad technical influence across multiple teams within our Engineering, CTO team. In this role you will work in a cross-functional team who are asked to solve a problem, rather than be handed a task to do. This is an excellent opportunity to work in a high-growth environment with a fast-paced and collaborative culture where you will have great opportunities to work on challenging problems.

•Lead in Design, analysis and documentation of products, systems or subsystems, setting the technical direction for key parts of the platform. •Provide hands-on technical leadership on the most complex areas of the platform, pairing with teams and unblocking hard engineering problems and raising the quality bar. •Take principal ownership of core framework components such as the workflow engine, rules/decision engine and event-driven orchestration layer, defining patterns and abstractions that other teams reuse. •Design and evolve event-driven architectures that support real-time decisioning, auditability and replay across multiple domains. •Lead the design and implementation of agentic AI–driven workflows, orchestrating services and AI components to assist human operators while keeping decisions explainable and controlled. •Define and own domain models, service boundaries and integration contracts, using techniques like domain-driven design and hexagonal architecture to keep systems loosely coupled and vendor-agnostic. •Drive engineering standards, tooling, and processes to the next level – from code quality and testing through to observability, reliability and security. •Develop and execute test procedures for software. •Proactively identify issues, bottlenecks, gaps, or other areas of concerns or opportunities and work to either directly affect change, or advocate for that change. •Work in an agile environment - Scrum or Kanban. •Document best practices, guides, systems design, reference architectures and implementations. •Participate in design and code reviews. •Contribute to the evolution of our architecture to make it more flexible and easier to use. •Be an ambassador for technical excellence both within Modulr and externally by representing Modulr in events and conferences.