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Location: Hybrid 2 days per week, based in Warsaw UoP (Contract of Employment) = 23,000 - 31,000 PLN per month gross B2B = 27,000 - 37,000 PLN per month net +VAT 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 Until now, insurers have been making billion-dollar decisions using outdated tools. 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. 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. 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. The Models team at hx is at the heart of our mission to empower customers with the tools to write, version, test, and visualise their models, directly impacting the core functionality of our platform. We are responsible for rearchitecting our technology stack to deliver features rapidly and securely, ensuring our services can handle increasingly complex and nested customer data. Our team blends deep technical skill with a culture of collaboration, ownership, and open communication. We work closely across disciplines, tackling complex data and performance challenges that drive real customer value. As a Senior Backend Engineer, you will play a pivotal role in improving the scalability and reliability of the Models service, accelerating delivery through well-designed abstractions and strong software architecture decisions. Your Senior Engineer responsibilities Designing and implementing scalable backend solutions that enable the Models platform to handle increasingly complex and nested customer data, directly improving reliability and performance. Addressing technical debt and driving forward-looking architectural changes to support rapid growth and evolving customer needs. Collaborating with cross-functional teams, including those working in Python, Rust and Kotlin, to deliver features that have measurable impact on customer experience and platform adoption. Architected and delivered complex backend systems with proven experience leading technical initiatives in Python Our teams use a combination of Python, Rust and Kotlin. Expect to be upskilled in Rust if you didnt already use it! We use AWS with ECS, EC2, Fargate, Lambda Designed and managed complex, arbitrary nested data structures tailored to diverse customer requirements. Demonstrated strong working knowledge of fundamental computer science and software engineering principles, including algorithms, data structures, complexity, design patterns, and architecture. Owned and delivered projects through the complete product development lifecycle, from conception to delivery. Technical Assessment: Bi-Directional Code Review (120 minutes)# At hyperexponential, we believe in a balance between remote work, and building relationships across teams and locations. You’ll have your main office in Warsaw, 2 days a week, with also ability to travel to London HQ to meet the wider team. International travel will be much less frequent, perhaps 2-3 times a year. Warsaw HQ was established in 2023, quickly hiring our first handful of high-calibre engineers. Fast-forward to today in 2025, there are 50+ in Warsaw and surrounding cities who travel for the collaborative environment. The office is also dog-friendly, so feel free to bring yours along! 25 days of non-working + Polish bank holidays ~£Optional for you: access to Private Healthcare via Luxmed + Multisport (fully funded by yourself as B2B Contractor)~ Top-spec laptop (MacOS or Windows) Contract of Employment (UoP)~ 26 days of holiday + Polish bank holidays ~ Private Healthcare Insurance via Luxmed ~ Top-spec work equipment (MacOS, Windows + additional monitors, mechanical keyboards etc)