There could be 2 ways to solve that specific problem of sending a welcome email: 1) Write a GraphQL schema stitching gateway, that can write a custom mutation

There could be 2 ways to solve that specific problem of sending a welcome email: 1) Write a GraphQL schema stitching gateway, that can write a custom mutation that delegates to another API (or GraphQL API) to write to the database, or writes to the database directly. This is becoming popular as more backend services expose their functionalities via GraphQL. 2) React asynchronously after the database write is done. Put the database event in a queue, for example, that runs the email send async-ly.