Comprehensive Explanation

Adobe Experience Manager uses Apache Jackrabbit Oak as its underlying content repository. Oak provides query indexes to optimize access to repository content without requiring expensive traversal operations.

A custom Oak index is defined through an index definition under the /oak:index repository hierarchy. The definition identifies the index type, indexed node types, relevant properties, and additional indexing behavior.

For Lucene indexes, the definition typically uses jcr:primaryType set to oak:QueryIndexDefinition , type set to lucene , and an appropriate asynchronous indexing configuration.

Option D correctly identifies the fundamental process of defining a custom Oak index.

Option A is incorrect because Sling servlets handle HTTP requests rather than establishing native Oak repository indexes.

Option B is incorrect because writing a Query Builder query does not automatically create the necessary custom index.

Option C is incorrect because Dispatcher manages HTTP request caching and filtering, not repository-level Oak indexing.

Cloud Service qualification: Adobe recommends maintaining custom index definitions in the application codebase and deploying them through Cloud Manager. Production developers should not manually create or modify index nodes through CRXDE Lite.

For AEM as a Cloud Service, index definitions are generally maintained under the project's _oak_index directory using versioned index names.

Official Adobe Reference: Oak Queries and Indexing; Indexing Best Practices in AEM.