At Build 2026, Microsoft is introducing Rayfin, an open-source tool that lets developers define and deploy complete backend systems. The solution runs on Fabric and offers built-in security, governance, and scalability.
While the rise of AI coding agents may have made application development child’s play, keeping those applications secure, compliant, and manageable once they go into production remains a challenge for many organizations. To address this, Microsoft is launching Rayfin: an open-source development kit that simplifies the backend development process by defining everything in code and deploying it directly on Fabric.
With Rayfin, developers can set up a complete backend system all at once, including databases, APIs, access policies, and business logic. The solution addresses the gap between rapid prototyping and actually bringing applications into production, which often requires manual integrations and compliance checks. This issue becomes even more urgent when applications connect to real-time business data.
Integration with Fabric
Rayfin turns backend development into a code-first workflow, allowing developers to describe and deploy the entire backend in code. The SDK and CLI enable users to define an application—including data models, APIs, authentication, and access policies—and deploy it with a single command to Microsoft Fabric, a data platform that competes with Snowflake and Databricks.
Once the application is running on Fabric, it immediately inherits enterprise-grade security, governance, and scalability. The application becomes a first-class artifact within the platform, connected to OneLake and directly usable for analytics and AI workloads. This eliminates the need to duplicate data or set up separate pipelines, which is traditionally a time-consuming and error-prone process.
Microsoft is partnering with Replit to offer developers the ability to build applications in an environment they already know, while the backend is securely and centrally hosted on Fabric. This combination of speed and governance particularly appeals to organizations that require both fast iterations and strict data control. Rayfin is available immediately via a GitHub repository.