Backend engineer in credit card payments

We're looking for a Senior Backend Engineer to join the Payments Infrastructure team. You'll design and build the payments platform behind iwoca's business credit card – the services that will approve each payment, monitor transactions for fraud, and pay out cashback.

• As a senior backend engineer, you'll own services and projects end to end, and shape the platform's architecture with the principal engineer, from service boundaries to how authorisation, rewards, and transaction monitoring fit together.
• You'll work closely with product to decide what the team builds and how.
• You'll help take it into production.
• Extending the service built to approve or decline each card payment in real time, using data held in other services. It places a hold on available credit in the ledger and applies iwoca's own checks, such as account status, merchant category code restrictions, and spend limits.
• Building the service that will screen card transactions for fraud and financial-crime risk as customers spend, so iwoca will rely less on third parties.
• Extending the service that will pay out cashback, as the team extends what else the card can offer.
• Designing sandbox tests that cover edge cases and failures across the card transaction lifecycle.
• Moving the card platform onto iwoca's own ledger and infrastructure with as little downtime as possible, then fixing the issues that only show up in production.

• You've designed and run highly available, low-latency payment systems in production, ideally on the issuing side.
• You've worked on card authorisation and clearing, and traced transactions from the terminal, through the acquirer and card scheme, to the issuer. You've used response codes to diagnose declined transactions.
• You have deep expertise in at least one object-oriented language. You've written and run backend services in it.
• You've built microservices, REST APIs, and asynchronous messaging with queues or topics, and designed the database schemas behind them, ideally in PostgreSQL.
• You've built agentic workflows, or used AI to scale your engineering output beyond what you could deliver alone, at work or in your own projects. You judge when to use it and when not to, and you check its output before it reaches production.
• You write and speak clearly, directly, and concisely. You adapt technical detail to your audience.
• Будет плюсом: You've worked on a ledger, reconciliation, or clearing system – for cards, loyalty points, bank transfers, or money remittance; You've written automated tests for payment systems, ideally test-first; You've used Python in production. It's the language the team works in

• We expect to pay from £100,000 to £120,000 for this role. But, we're open-minded, so definitely include your salary goals with your application. We routinely benchmark salaries against market rates, and run quarterly performance and salary reviews.
• Flexible working hours.
• Medical insurance from Vitality, including discounted gym membership.
• A private GP service (separate from Vitality) for you, your partner, and your dependents.
• 25 days’ holiday per year, an extra day off for your birthday, the option to buy or sell an additional five days of annual leave, and unlimited unpaid leave.
• A one-month, fully paid sabbatical after four years.
• Instant access to external counselling and therapy sessions for team members that need emotional or mental health support.
• 3% Pension contributions on total earnings.
• An employee equity incentive scheme.
• Generous parental leave and a nursery tax benefit scheme to help you save money.
• Electric car scheme and cycle to work scheme.
• Two company retreats a year: we’ve been to France, Italy, Spain, and further afield.
• A learning and development budget for everyone.
• Company-wide talks with internal and external speakers.
• Access to learning platforms like Treehouse.
• Offices in London, Leeds, Berlin, and Frankfurt with plenty of drinks and snacks.
• Events and community-led groups, including running groups, padel, and monthly ping-pong and pool competitions.