About this role.
Masabi is hiring a Principal Engineer to provide architectural and technical leadership for its payments platform supporting large-scale public-transit fare collection. The role combines domain expertise in payment processing, PSP and acquirer integrations, EMV/contactless flows, and distributed systems design. This engineer will influence multiple teams, set standards, review designs, resolve complex reliability and scalability issues, and contribute hands-on when necessary. The position is UK-remote, with optional hybrid work in London, and emphasizes AWS, microservices, operational resilience, and long-term platform evolution.
Role DNA
A quick view of the complexity, pace, ownership and collaboration implied by the job description.
Job Complexity
5/5Pace & Pressure
4/5Autonomy Level
5/5Communication Load
5/5Salary analysis
Estimated compensation compared with the broader US market for similar roles.
Core skills
Skills and capabilities most closely associated with this opportunity.
Sample interview questions
I would begin by mapping authorization, capture, settlement, reversals, and exception paths, then define clear idempotency keys and state transitions. I would use asynchronous, durable messaging where appropriate, isolate external-provider failures with timeouts and circuit breakers, and maintain an auditable transaction ledger. The design would include reconciliation processes, observability, and carefully tested recovery behavior for duplicate, delayed, or failed events.
I make the trade-offs explicit by assessing customer impact, operational risk, cost, reversibility, and future constraints. When a short-term solution is justified, I document the technical debt, establish ownership, and create a measurable follow-up plan. I also seek incremental designs that deliver value now while moving the platform toward the intended architecture.
I first validate functional requirements, supported payment methods, regional constraints, security obligations, SLAs, and failure semantics. I would build an adapter behind a stable internal payments abstraction, use sandbox and contract testing, and ensure that idempotency, retries, webhooks, reconciliation, and observability are designed before production launch. I would also establish clear operational escalation paths with the provider.
I would monitor authorization success rate, latency by payment flow and provider, error and timeout rates, duplicate-processing incidents, reversal and reconciliation exceptions, queue lag, and availability. I would segment metrics by geography, provider, payment method, and release version to reveal localized issues. Business-facing dashboards should also track completed journeys and the financial impact of payment failures.
I establish principles, reference architectures, and decision-making forums that let teams act independently within clear guardrails. I engage deeply on high-risk or cross-cutting decisions, provide concise written feedback, and coach senior engineers to own designs in their domains. This creates alignment and raises engineering capability while reserving principal-level involvement for decisions with the largest system-wide impact.
About Us_
// At Masabi, we’re driving the fare payment revolution, powering the journeys of millions all over the world. We build fare collection platforms that allow riders to seamlessly buy and present tickets for public transport either on their mobile phones, from a ticket machine, or even by tapping their bank card to travel.
Our Justride platform is used in over 250 locations globally, including some of the largest cities in the world. With our industry-first mobile ticketing SDK, we’ve partnered with large players in the transport space, including Uber, Moovit and Transit.
Your own journey is important to us too. Choosing a role here means joining a network of innovators from all walks of life; a group of passionate individuals who consistently deliver. Here, you’ll find the tools you need to build the career you want. Whether you’re taking the direct route or trying a new path, we’ll support you no matter what.
The Role_
// We’re looking for a Principal Engineer – Payments to join Masabi’s Architecture team, with a primary focus on our payments domain.
This is a senior role for someone who combines strong technical judgement with deep payments experience. You’ll shape the technical direction of our payments platform while staying close enough to the detail to design, review and support meaningful technical work.
Working across the engineering organisation, you’ll act as a senior technical leader within the payments domain: contributing to architecture, guiding complex decisions and helping teams build scalable, resilient systems that support millions of journeys worldwide.
The role suits someone who can move between system-level thinking and implementation, who understands trade-offs, can navigate ambiguity and helps turn complex or loosely defined problems into clear, practical technical approaches.
Location_
// This role is open to candidates based anywhere in the UK, with the flexibility to work fully remotely. For those based in or around London, we also offer the option of hybrid working from our London office.
Responsibilities_
Shape the technical direction of Masabi’s payments platform, contributing to architecture, standards and engineering best practices
Design and deliver scalable, secure, resilient and cost-effective payment solutions aligned with Masabi’s platform direction
Support teams in building towards a modern, microservices-based architecture while balancing delivery priorities and long-term platform health
Stay close to technical delivery through architecture reviews, design discussions and targeted hands-on contribution where needed
Identify and work through complex technical challenges related to scalability, resilience, operational performance and system evolution
Act as a senior technical advisor across engineering teams, supporting and influencing technical decisions, particularly within the payments domain
Work with external providers and payment partners on integrations, technical alignment and problem-solving
Contribute to technical roadmap planning, prioritisation, technical scoping and architecture discussions for complex initiatives
Produce clear technical documentation and contribute to engineering standards, technical forums and good practices across the organisation
About You_
// You bring a mix of strong technical expertise, sound judgement and real-world payments experience.
Strong experience working on payment systems, including integrations with PSPs, gateways, EMV, contactless EMV, acquirers, etc.
Good understanding of payment flows, transaction lifecycles and system design considerations
Experience designing and evolving distributed systems and microservices architectures
You’ve operated at Principal or Staff level, shaping technical direction across multiple teams or domains
Strong judgement and the ability to balance short-term delivery with long-term architectural outcomes
Comfortable navigating ambiguity and turning complex problems into clear, practical technical approaches
Clear and thoughtful communicator, able to engage both technical and non-technical audiences
Comfortable being hands-on where needed, while maintaining a focus on system-level impact
You have strong experience with cloud platforms (AWS preferred) and modern infrastructure practices
You’ve worked on systems where scale, reliability, performance and cost trade-offs matter, and can navigate those decisions thoughtfully
You’ve contributed to engineering standards, architecture patterns or platform direction
Interest in or exposure to AI-enabled systems, particularly understanding architectural implications in production
Nice To Have_
Experience with transit systems or fare payment systems (e.g. tap-to-ride systems)
Familiarity with card schemes (e.g. Visa, Mastercard, Interac)
Experience working in complex, multi-service or event-driven architectures
Familiarity with a range of tools and technologies including:
Development: Kotlin, Java
Data storage: DynamoDB, MySQL
Infrastructure as code and CI/CD: Terraform, GitLab CI/CD
// You don’t need to have experience in every area listed above. If you bring strong fundamentals, good judgement and a willingness to learn, we’d still love to hear from you.
Some of Our Benefits_
25 days of holiday per year plus the option to buy another 5 days pro-rated
Private Healthcare via AXA, including pre-existing conditions and mental health
Life Insurance
Menopause support
Choice of workstation
Ability to work for up to 3 months per year from any country in the world (certain limitations)
Pension scheme
Training allowance of up to £1000 per year
£200 annual allowance for any home office need or improvement
Enhanced family leave pay
Cycle to work scheme
Regular social gatherings with a monthly allowance for each employee
Fun and collaborative environment with a focus on making a difference in the world
Careers at Masabi are for people going places – driven by a mission to make transit fair and accessible for all.
// We are a network of innovators from all walks of life, passionate about making a difference. At Masabi, we operate with openness and trust, creating an environment where everyone feels empowered to bring their whole, authentic selves to work.
Whoever you are, just be yourself.
// We welcome applications from underrepresented groups, including disabled and neurodivergent people, and can make adjustments at any stage of the process. You’re also welcome to share your pronouns whenever you feel comfortable. Together, we simplify journeys, remove barriers, and improve daily life for millions.
Why Join Masabi?
Driven by Purpose – We believe in journeys made simple. The work isn’t always easy, but the best things never are.
Encouraged to Accelerate – Masabi is going places and our people are in the driving seat. Whether you’re taking the direct route or exploring new paths, we support your journey.
Advancing with Empathy – We put people first and foster a culture of learning, not blame. No matter your cargo, we share the load.
We’re already powering journeys – are you ready to join us?
Annual salary information is not provided for this position. Explore salary ranges for similar roles in our Salary Directory ›
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