Platform & Security Engineer

Platform & Security Engineer

London, England, United Kingdom; UK (Remote)

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 regular patching cadences
• Support operational resilience (OR), disaster recovery (DR), backup strategies, and business continuity planning
• Help maintain and improve security and compliance processes aligned with ISO27001 framework

System Reliability & Observability

• Improve system reliability, scalability, resilience, and performance across the Mast platform
• Troubleshoot infrastructure, platform, networking, and security related issues across environments
• Contribute to incident response processes and ongoing operational improvements
• Build systems and tooling that automate infrastructure management and operational workflows wherever possible
• Implement and maintain observability tooling including monitoring, logging, alerting, and tracing

Developer Experience (DevEx)

• Building tools and platforms that enable product teams to provision resources autonomously (self-service)
• Building and maintaining CI/CD pipelines and deployment workflows to improve developer experience and delivery velocity
• Introducing guardrails for self-service cloud engineering by development teams

Requirements

• 5+ years experience in either platform engineering, cloud infrastructure, SRE, DevOps, or security engineering roles
• Strong experience with AWS and container based infrastructure
• Experience managing infrastructure using Infrastructure as Code tools such as Terraform
• Experience building and operating scalable, reliable production systems
• Experience with CI/CD pipelines, deployment automation, and developer tooling
• Working knowledge of Linux/Unix systems, networking, and cloud security fundamentals
• Experience with observability tooling including monitoring, logging, alerting, and tracing
• Experience supporting incident response, operational resilience, disaster recovery, or business continuity processes
• Comfortable working across infrastructure, security, reliability, and compliance domains
• Comfortable owning operational and infrastructure concerns end-to-end in a fast moving environment
• Strong communication skills and ability to collaborate effectively with both technical and non-technical stakeholders
• Comfortable using AI tools as part of your development workflow

Desired Attributes

• Thrives in fast-paced startup environments with a strong sense of ownership and urgency
• Pragmatic and solutions oriented, with strong execution skills
• Strong operational mindset and calm under pressure during incidents
• Self directed, highly organised, and capable of driving initiatives independently
• Curious and adaptable, with a continuous improvement mindset
• Focused on building practical, scalable systems that improve operational efficiency and developer experience
• Experience with Ruby on Rails applications and infrastructure is highly desirable

Salary & Location

Location: London or UK Remote

Salary: £90,000 to £100,000 + Stock Options

• Stock Option Plan
• 25 days holiday + bank holidays
• 4 - 10 weeks work from anywhere, based on tenure (for UK based roles)
• Vitality Health insurance
• Pension plan
• Equipment budget
• Learning & development budget
• Cycle to Work Scheme
• Monthly team socials + Quarterly Team Meet-ups @ HQ
• Digital-first, employee-first company with a flexible working culture + Central London HQ

Mast. is an equal opportunity employer and we celebrate diversity and are committed to creating an inclusive environment for all employees.