Software Engineer

Build a payments platform from a blank pagenumi is partnering with a major UK payments business that is being carved out of a tier 1 bank to become a standalone technology company. It already handles a huge share of UK card payments every day. Now it is rebuilding the technology behind them, from scratch.This is not a legacy banking role. The old mainframe and batch estate stays behind. In its place: a cloud-native, event-driven platform, built by a permanent engineering team that will grow to 100–200 engineers. The people who join now will shape how that team works.The engineering

• Kotlin for ~90% of the back end, Rust where it's time-critical and must be provably correct
• TypeScript, React and React Native on the front end
• AWS, Kubernetes, Istio, NATS and Databricks
• Event-driven and real-time: no batch jobs, async wherever possible
• Continuous delivery: 46 engineers averaged ~60 deploys a day ahead of the first production releases
• The aim is that every engineer ships to production on day oneWhat you'll do
• Design, build and run production services, end to end
• Shape technical decisions, architecture and engineering standards
• Work in cross-functional, outcome-aligned teams that choose their own ways of working
• Help build the culture of a brand-new engineering organisationHiring is open across the full ladder, from Associate to Principal. You don't need to pick a level: it's calibrated with you through the process.What they're looking for
• Distributed systems experience in a cloud-native, event-driven, continuously delivered environment
• Kotlin or strong JVM experience (an interest in Rust is a bonus)
• You've built something from zero: a product, platform, team or capability
• Comfortable with ambiguity and making progress on imperfect information
• Low ego: confident enough to hold an opinion, humble enough to change itPayments experience is not required. The environment you've worked in matters more than the logo on your CV.The processFourteen days from first conversation to offer: a call with numi, a remote interview, a take-home exercise (AI tools welcome, as long as you can explain every line), then an in-person final.Salary: £60,000 – £120,000+ depending on level. London, hybrid (2–3 days in office).Please note: visa sponsorship is not available.Interested? Apply here.