Senior Full-Stack Engineer (Browser Extensions & APIs)

We are a fast-growing, bootstrapped cybersecurity startup building lightweight, privacy-first browser protection tools. You'll work directly with our Fractional CTO and Principal Engineer to build and maintain Manifest V3 browser extensions alongside the real-time backend that powers them. Key Responsibilities Build and maintain Manifest V3 browser extensions across Chromium (Chrome, Edge, Brave) and Firefox Design and implement content scripts, service workers, and secure cross-origin communication Build and maintain low-latency Node.js/TypeScript backend APIs for real-time URL and script scanning Integrate with third-party threat intelligence APIs Manage deployment and review cycles for the Chrome Web Store and Firefox Add-ons marketplace Work with AWS or GCP infrastructure and relational/non-relational databases Ship independently with high autonomy — no PM layer, direct collaboration with the Fractional CTO and Principal Engineer Requirements 3+ years hands-on experience shipping browser extensions, deep Manifest V3 knowledge required Strong Node.js/TypeScript backend experience Solid understanding of browser security models, DOM manipulation, service workers Experience with AWS or GCP, relational and non-relational databases Comfortable working with high autonomy and minimal process Available to work with meaningful overlap with UK business hours (GMT+0) for code reviews and collaboration Engagement: