“Under-the-hood of GraphQL”-look at the execute req part of the query lifecycle

There are of course several implementations though it seems the Apollo framework dominates. I've been using the Expedia implementation for Kotlin & Spring Boot lately, which uses the graphql Java implementation. While not perfect, it's a pretty nice implementation and really easy to get started with if you already use Spring Boot. It basically autoconfigures when you add the dependency to your classpath (and get rid of some conflicting ones). It then generates graphql end points for any spring bean implementing the Mutation or Query endpoints. You don't write a single line of schema; it's all generated.