Platform&SecurityEngineer

Mast is on a mission to make complex lending simple. The UK's specialist lending market is underserved by technology, with legacy systems that can't handle the nuance of complex income, niche products, or the broker workflows that specialist lenders rely on. We're building modern, cloud-native lending technology, purpose-built for specialist lenders, that helps them process more applications in less time, reach decisions faster, and deliver better experiences for brokers and borrowers. We're pioneering the use of AI in mortgage origination, building it into the platform from the ground up rather than bolting it onto legacy architecture.. We work with regulated lenders across the UK, have a 100% delivery track record, and are building a high-performance team where everyone has real ownership and direct impact. We're looking for a Platform & Security Engineer to help scale and secure the Mast platform as we continue to grow. This role combines platform engineering, cloud infrastructure, security, reliability, observability, operational resilience, and compliance. You'll work closely with the Head of Engineering to improve developer experience, modernise infrastructure, strengthen our security posture, and ensure our systems remain reliable and resilient as we onboard more clients and ship more features. This role is suited to an experienced engineer comfortable owning infrastructure, security, reliability, and operational resilience across production systems in a fast moving startup environment. Responsibilities Cloud & Platform Own and maintain cloud infrastructure across AWS and container-based environments Design, build, and maintain infrastructure using Infrastructure as Code tools such as Terraform Support with future replatforming and infrastructure modernisation initiatives, including migration from Heroku to AWS container platforms Security & Compliance Manage vulnerability remediation processes including CVE tracking, security patching, and maintaining regula