How does the Abstract Syntax Tree (AST) work in GraphQL?

The AST is a programmatic, tree-like representation of the incoming GraphQL query string generated by the parser.

When a server receives a query, it parses it into an AST, validates the AST against the schema, and executes it. Resolvers can access the AST via the info argument (the fourth parameter). Analyzing the AST allows for advanced optimizations like Lookaheads (seeing what child fields were requested before executing the DB query).