How We’re Surviving 20+ Domains and 100+ SQL Tables While Migrating Our Legacy .NET Backend to GraphQL

Introduction In Part 1 – How We’re Surviving 600+ Legacy Angular Components While Migrating to Next.js, GraphQL, and a Monorepo , we explored how we are modernising a large Angular frontend incrementally. We are doing this by using Next.js for modern React rendering, GraphQL for flexible data querying, a monorepo to coordinate code across teams, web components for reusable UI, and generative AI to help understand complex legacy code. This approach avoided a risky “big bang” rewrite while enabling continuous delivery of new features. However, the frontend is just half the picture. Behind it runs a large .NET 6 serverless backend, responsible for critical workflows like user registration, subscription management, and reporting. Migrating this backend required careful planning to reduce risk and ensure business continuity, so we applied a similar philosophy: incremental modernization using a monorepo, GraphQL, and AI assistance. The Legacy Backend We Started With Our backend is a mature .