Full Stack Engineer (Kotlin/React)

About hyperexponential (hx) At hyperexponential, we’re building the AI-powered platform that enables the world’s most critical decisions in a $7 trillion industry, which risks to take, and how to price them. These are the decisions that shape real-world outcomes: whether rockets successfully launch into space, autonomous vehicles make it to market, or communities recover after major storms. Until now, insurance has been making billion-dollar decisions using outdated tools. We’re changing that. Our platform brings together data, AI, and human expertise to give insurers the fastest path from submission to decision - helping them move faster, act smarter, and take on more risk with confidence. Backed by a16z, Highland Europe, and Battery Ventures, we’re scaling globally - already trusted by nearly 50 of the world’s largest insurers, with zero churn and billions in premiums flowing through hx. What began as a single product in one market has rapidly evolved into a multi-product, multi-territory platform powering every stage of pricing and underwriting. AI is at the core of what we do - from building the world’s first domain-specific AI peer programmer for insurance (think GitHub Copilot with a PhD in actuarial science) to shaping agentic workflows that reinvent how this industry operates. What makes hx different is the people who build it. Here, impact isn’t tied to title or tenure; it’s defined by the challenges you take on and the discipline you bring. Surrounded by peers who stretch you, you’ll do the best, hardest work of your life in a company engineered to endure. If that sounds like you, join us in building what comes next. About the Core Services team The Core Services team exists to accelerate product development across hx by building the foundational capabilities that every product team depends on. Our work sits at the intersection of platform engineering and product enablement, ensuring that teams can move faster while maintaining high standards of security, scalability, and customer experience. We build and operate reusable platform services such as authorisation, webhooks, notifications, API documentation, and API proxy infrastructure. These services form the backbone of the hx platform, enabling teams to focus on solving complex insurance problems while relying on robust shared systems for identity, access, and integration. As a Software Engineer in the Core Services team, you will help design and deliver the next generation of platform capabilities at hx. This includes building a scalable permissions and authorisation service, defining how product teams integrate with it, and ensuring that the systems we build enable both internal teams and customers to move faster with confidence. What you’ll be doing Design and deliver a scalable authorisation service that enables granular permissions across the hx platform, supporting product teams building complex underwriting workflows. Define and validate a granular permissions model in collaboration with product and engineering teams, ensuring it supports teams, roles, risk, privacy, and model access across the platform. Build reusable platform services and SDKs that allow downstream teams to adopt core capabilities quickly, accelerating delivery across multiple product areas. Develop infrastructure and APIs for platform capabilities such as authorisation, webhooks, notifications, and API proxy services, ensuring they are secure, resilient, and easy to integrate. Partner closely with application teams to support adoption of the new permissions service, delivering an MVP that integrates with at least one production application. Contribute to engineering culture through strong operational discipline, clear documentation, and collaboration that raises the standard of platform engineering at hx. What you’ll need to have done Built and delivered backend or infrastructure services that enabled multiple teams to ship faster through reusable platform capabilities. Designed and implemented APIs or platform services that achieved high reliability, scalability, and maintainability in production environments. Delivered systems using Rust or Kotlin (or a JVM language) and demonstrated the ability to learn and apply new technologies when required such as Frontend exposure with React/TypseScript. Implemented infrastructure using Terraform or other infrastructure-as-code tooling to support scalable cloud deployments. Delivered systems on cloud platforms such as AWS , ensuring operational robustness, observability, and long-term maintainability. Collaborated with cross-functional teams to design solutions, write clear documentation, and drive successful adoption of shared platform services. You’re unlikely to thrive here if You prefer highly defined problems and predictable delivery environments rather than working through ambiguity and shaping new platform capabilities. You focus only on your own component rather than taking responsibility for the wider outcome and adopti