Coursera's platform is composed of hundreds of APIs, implemented across dozens of services by various engineering teams. Our client engineers have faced many challenges while using these APIs, especially around discoverability and assembly of data from various services. We’re working to solve these problems by migrating all client data access from REST to GraphQL.

Our path to GraphQL is different than most -- instead of manually adapting each of our REST APIs for GraphQL, we built a dynamic assembly layer that unifies our distributed APIs into a single GraphQL endpoint and corresponding schema. This unified schema allows clients to access data from across our various services in a single query.

In this talk, I’ll cover why we’re transitioning to GraphQL, share challenges and learnings from building our GraphQL assembly layer, and discuss a few open questions we have around designing APIs for simultaneous REST and GraphQL usage, and who owns the business logic in GraphQL.