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API Design · easy

3. Mutations, Variables, and Input Validation

Changing server state safely through typed operations.

1 min read3 questionsup to 50 XPtopic 3/5

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GraphQL mutations describe writes such as creating a transfer or updating a profile. Variables keep values separate from the operation document and let the server validate them against input types.

The schema validates shape, but it cannot decide whether a caller has permission to transfer a particular asset. Authorization and business rules still belong in the resolver or service layer.

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Check your understanding

  1. 1. Why use GraphQL variables instead of interpolating values into a query string?

  2. 2. What does an exclamation mark mean in `CreateTransferInput!`?

  3. 3. Where should permission checks happen?

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