Questions
6 of 10
What are object types?
Difficulty: 5/10
object types, schema design, type system
The most basic components of a GraphQL schema are object types, which just represent a kind of object you can fetch from your service, and what fields it has.
- 1
Most of the types you define in a GraphQL schema are object types.
- 2
An object type contains a collection of fields, each of which has its own type.
Two object types can include each other as fields, as is the case in our example schema from earlier:
Scenario Questions
0-2 years experience
- 1We need to add a new entity called `Book` to our GraphQL API. How would you define its object type and what fields would you include?
- 2If a client queries a field that isn’t defined in an object type, what response does GraphQL give and why?
2-5 years experience
- 1Our product team wants to expose a `User` type that includes a list of `Order` objects, but some orders are fetched from a legacy microservice. How would you model the object types and resolve the nested data?
- 2During a recent deployment, queries that requested the `price` field on the `Product` type started failing with a validation error. Walk me through how you would debug the issue related to object type definitions.
5-8 years experience
- 1We’re planning to split our monolithic GraphQL schema into multiple federated services. What considerations around object types and their extensions should we keep in mind to avoid breaking existing clients?
- 2Our API receives high‑traffic queries that request deeply nested object types, causing performance bottlenecks. How would you redesign the object type hierarchy or resolver strategy to mitigate this at scale?
8+ years experience
- 1Our organization is migrating from a custom REST contract to a GraphQL API that must serve dozens of downstream teams. How would you establish a governance model for defining and evolving object types to balance flexibility and backward compatibility?
- 2We need to support versioned object types (e.g., `UserV1`, `UserV2`) across multiple services without duplicating schema definitions. What architectural patterns would you employ to manage this complexity long‑term?
Follow-up Questions
- Can you give an example of how you’d add a new field to an existing object type without breaking clients?
- What are the trade‑offs between using interfaces versus extending object types in a federated schema?
- How do you handle circular references between object types in your schema?