Senior Backend Engineer

Senior Backend Engineer | Hybrid | Cyber security | £90k - £105k A criminal buys a phone number, sends ten thousand texts pretending to be a bank, and moves on before anyone notices. Someone has to find that number, prove it is being used for fraud, and get the carrier to switch it off. That is this job. You will be the engineer behind a product that does this at scale, for the banks, retailers and couriers whose names keep getting borrowed. It is Go, on AWS, with an older codebase you will help retire and an internal interface in TypeScript. The part that makes this role unusual is the domain. When a customer insists a number cannot have been spoofed, you are the one who works out whether they are right, which means understanding how numbers route, where the trust boundaries sit between operators, and what a network actually tells you when you probe it. You will pick up questions from account managers and, occasionally, customers, and you will bring problems into planning rather than waiting to be handed tickets. What we are looking for Production backend engineering, ideally Go. Strong engineers from Python, Java or another backend language will be considered where the domain knowledge is there.Real exposure to phone networks, messaging or number infrastructure, from a carrier, a VoIP or CPaaS business, or a fraud and abuse team.Comfort owning services in production: reliability, cost, and the boring parts.The ability to explain a technical answer to someone who is not an engineer, and be right. Useful but not required Voice and messaging protocols, number routing, rich messaging standards. Legacy scripting languages. Containers and orchestration. Relational databases at scale. A background in fraud, abuse or security.