In AEM, Lucene is often used for indexing due to its powerful full-text search capabilities, and it also supports asynchronous indexing. Asynchronous indexing allows the system to handle other tasks while indexing is being processed in the background, which can improve performance and scalability. This is especially useful when multiple properties need to be indexed without impacting the immediate response times of the system. Therefore, when a developer needs to enable the indexing of multiple properties asynchronously, a Lucene index is the most suitable choice.