Questions
4 of 10
What are Enum types?
Difficulty: 5/10
enum definition, schema evolution, federation consistency
Enum types, also known as enumeration types, are a special kind of scalar that is restricted to a particular set of allowed values.
This allows you to:
- 1
Validate that any arguments of this type are one of the allowed values
- 2
Communicate through the type system that a field will always be one of a finite set of values
Here’s what an Enum type definition looks like in SDL:
Scenario Questions
0-2 years experience
- 1We need to add a new status field to our GraphQL schema that can only be 'OPEN', 'CLOSED', or 'PENDING'. How would you define this using an enum, and what would a client query look like?
- 2If a client sends a value not listed in the enum, what does GraphQL do, and how would you handle that in your resolver?
2-5 years experience
- 1Our product team wants to deprecate the 'PENDING' value in the OrderStatus enum and replace it with 'IN_REVIEW'. How would you modify the schema to support this change without breaking existing clients?
- 2During testing we noticed that a mutation is failing because the enum value sent from the frontend is in lowercase ('open' instead of 'OPEN'). How would you debug and fix this issue?
5-8 years experience
- 1We have a federated GraphQL architecture with multiple services each defining overlapping enums. What strategies would you use to keep enum definitions consistent across services, and what are the trade‑offs?
- 2A high‑traffic query includes an enum filter on a large dataset, and we see performance degradation. How would you investigate whether the enum is causing the issue and what optimizations could be applied at the schema or resolver level?
8+ years experience
- 1Our organization is migrating from a monolithic GraphQL server to a micro‑service mesh. How would you approach versioning and evolving enums across many teams to avoid breaking changes over time?
- 2We need to expose a public GraphQL API while maintaining internal enums that include sensitive internal states. How would you design the schema to hide internal enum values yet keep the internal services functional?
Follow-up Questions
- What happens if you omit the enum definition entirely and use a string instead?
- Can you explain the difference between deprecating an enum value and removing it?
- How would you test that your enum changes don’t break existing clients?