Principal Engineer

•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.

About Us
At Modulr our mission is to move money efficiently to power business productivity. We are building a new digital payments service to make money flow more efficiently through businesses and the economy. This is a new type of payments account that is built for businesses that need faster, easier and more reliable ways to move money.
Our flexible platform and innovative approach allows our customers to utilise our payments account instead of a traditional bank account. Our accounts come with a sort code and account number, access to payment systems (eg Faster Payments and Visa) and everything our customers need from a payments account. They can instantly open as many accounts as they need, automate how they make and receive payments as well as the reconciliation processes these create. All in real time, 24/7 through their own systems utilising our API that integrates into any platform.
Our founding team has a wealth of experience in the payments industry and growing successful businesses. Modulr is backed by payments giants PayPal Ventures and FIS Ventures, as well as startup and scale up specialists Blenheim Chalcot, General Atlantic, Frog and Highland Europe which enables us to leverage their resources and expertise to drive our growth initiatives. These partnerships provide us with the necessary provisions to propel our business to new heights.

Modulr values
•Building the extraordinary and going that extra mile
•Owning the opportunity, be passionate and proud of the time you invest
•Move at pace, reach your goals faster with us supporting you each step of the way
•Achieve it together, working as a team and being a Modulite

The Tech Team
At Modulr we are focused on building autonomous squads that are focused on working in the best possible way. We operate in a tribes and squad model with each area focused on a particular growth area. Each squad is small and cross-functional. We have big ambitions and have many interesting challenges ahead. Our strategy is to provide our customers with seamless connectivity into payment schemes both domestically and overseas no matter where they're based.

About the role
•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.

About You
•Able to clearly communicate architectural goals and standards.
•Ability to deep dive into technical problems and customer led challenges
•Strong analytical thinking, problem-solving, appropriate judgement and decision-making skill
•Commitment to collaboration and teamwork
•Proven ability to effectively manage timelines and deliverables
•You thrives in complex, rapidly changing environments and can make sound judgements amid ambiguity
•You are a self-starter, motivated team player who thrives in a fast-paced environment
•You enjoy shaping architecture as well as code – guiding service boundaries, contracts, writing complex frameworks and event models that other teams build on.
•You have a strong track record of building high-scale, reliable systems, and you are comfortable designing for resilience, observability and graceful degradation from day one.
•You are comfortable in building event-driven and data-driven platforms.
•You are curious/passionate about AI and automation and think carefully about where agents/LLMs add real value while staying within risk and control boundaries.

Technical knowledge required
•Expert in Java with deep experience building and operating distributed microservices in a cloud environment, at scale
•Expert in OOPs and design patterns.
•Expert in REST API design.
•Strong practical knowledge of event-driven architectures.
•Open-Source technologies, such as Spring and Hibernate.
•Strong background in observability and reliability
•Open-source RDBMS technologies such as PostgreSQL
•Experience testing across different levels of applications and advocate for best practice.

Nice to have
o Experience with compliance / risk / FinCrime domains
o Hands-on experience designing or integrating workflow engines.
o Experience with rules / decision engines and a clear view on how to manage rule lifecycle, versioning and testing at scale.
o Experience/understanding of agentic / AI-driven systems and how to integrate them into backend workflows with appropriate guardrails, monitoring and fallbacks.
o Exposure to payment schemes/flows, regulatory frameworks, SME/partner onboarding; experience reducing false positives via rule tuning/enrichment; familiarity with schema governance and data‑lineage tooling is a strong plus.

ModInclusion
We believe that by seeing Modulr, and the world, from all sorts of angles, we can make life better for all. We want you to know that the things that make you, you — like your identity, age, ability, and background — are things that we will always celebrate and support with open arms. As such, we are keen to maximise the diversity of our workforce and actively encourage applications from anyone and everyone.