Full-Stack Developer (React / .NET Core / Azure)

They are building a premium web platform from a completely blank canvas to serve as the single digital front door for their entire multi-million-pound business. This is a pure product-led platform focused on consumer-grade user journeys, exceptional scalability, and elite modern engineering standards. This is not an internal enterprise IT or ERP implementation role-it is a rare chance to play a definitive role in shaping a flagship public-facing digital platform from day one., The Role & Team Focus: We are looking for two highly competent Full-Stack Developers to act as the core "doers" and technical engine room of a tightly focused, elite four-person product squad.

The defining engineering focus for these positions is data aggregation. You will be responsible for pulling varied services across the wider business into a single place, taking large volumes of data from modern data lakes, and presenting it cleanly through a fluid, premium public interface. A significant portion of this role involves engineering heavy API connections, webhooks, and secure data workflows to seamlessly connect the new platform to the wider estate and external partners. Given the nature of the data handled, you must be thoroughly well-drilled in security and safe coding practices.

Core Technical Stack: To be successful in this role, you must bring active, commercial fluency across the following stack:

• Frontend: Highly competent in React on the frontend, alongside Next.js and Node.js.
• Backend & Cloud: Strong experience with C# .NET, ASP backend, Microsoft SQL, and Azure SQL.
• DevOps & Workflow: Working natively against an Azure estate utilizing Azure DevOps pipelines.
• Integration Engines: Deep understanding of headless, API-first product designs, webhooks, and microservices.

What We Are Looking For

• Stack Competency: Proven commercial experience balancing C# .NET backend engineering with modern React frontend development.
• Transactional Pedigree: Experience handling high-volume transactional data, ideally within highly regulated environments such as financial services, fintech, life sciences, or healthcare.
• Product Craft: The strongest signal is someone who has not only built internal tools but has turned complex logic into a beautiful product live in the public domain.
• Aggregation Mindset: A strong understanding of modern data ecosystems, tools like Snowflake, or data lakes, with the ability to build robust API integrations.
• Logistical Fit: Must be based in the UK with the right to work, and fully comfortable travelling to the London King's Cross office 4-5 days a month

If you are a driven full-stack engineer who wants to leave their fingerprint on a greenfield codebase and build a premium digital product from scratch, we want to hear from you.

The Opportunity: Keystream is partnering with a major global diagnostics and healthcare organisation that is investing heavily in bootstrapping a brand-new, flagship digital product division from scratch.