PUT is idempotent, so repeated calls create or fully replace the index definition at the specified URI without duplicating resources. POST would create a new index each time, failing the create-or-update requirement, while PATCH performs partial updates only.
Why this answer
Azure AI Search exposes index definitions through its REST API at /indexes/{indexName}, and creating or replacing an index definition uses HTTP PUT. PUT is idempotent and replaces the entire index definition, which is the documented method for creating or updating an index. GET retrieves, PATCH is not supported for index definitions, and DELETE removes the index.
Exam trap
AI-200 often tests whether candidates assume PATCH is available for partial index updates, when Azure AI Search requires PUT with the complete definition.
How to eliminate wrong answers
Option A is wrong because GET only retrieves an existing index definition and cannot create or update one. Option C is wrong because Azure AI Search does not support PATCH for index definitions; partial updates are not available via PATCH on the indexes endpoint. Option D is wrong because DELETE removes an index and does not create or update it.