The Schema: SDL & the Type System
Model the tracking view in SDL and make one canonical schema the contract both stacks export and are checked against.
SDL and the type system in depth
The kinds of type a GraphQL schema is built from (scalars, enums, objects, interfaces, unions, input types and their wrappers), how a selection maps onto them, and how SmallRye and Strawberry express each one code-first.
Nullability and null propagation
What a null means in a GraphQL response, how list and non-null wrappers decide where a failure lands, and how the tracking schema places its nullable fields so one failed source costs a field instead of the page.
Schema-first / contract-first
How the tracking view keeps two code-first schemas aligned with one canonical SDL: export each stack's schema, diff it in two directions with GraphQL Inspector, lint the contract, and watch seeded drift fail the gate.