As you review your incident ticket volume, you realize that there is an upward trend observed in the incidents regarding Azure Cognitive Search queries. Following the next practices, you can identify and address the performance concerns. Review the answer choices below and choose the options that you will prefer to improve Cognitive Search queries performance. Keep the operational costs low. (select two answer choices) 

Answer options:

A.Reduce the content to maintain smaller indexes
B.Select all properties of the fields while creating a search index
C.Provide additional storage by adding disks
D.Mapping a complex data type to a simpler type field
E.Upgrade to standard S2 storage and add additional search units

Correct Answers: A and D
Option A is correct because smaller indexes would bring in faster query results. As data grows, the index becomes large, thereby slowing the search queries.
Option B is incorrect because selecting fewer properties or only the properties that you need would improve query performance.
Option C is incorrect because adding additional disk would not improve query performance. It would also increase your operational cost.
Option D is correct because complex data types require additional storage and hence increases your operational cost. However, if there is an opportunity to map a complex data type to a simpler type field, you can save additional storage and resource cost while maintaining the search query performance.
Option E is incorrect because upgrading to standard S2 storage and adding additional search units will increase the operational costs.
Reference:
To learn more about performance tips of cognitive search index, use the link given below: 

https://docs.microsoft.com/en-us/azure/search/search-performance-tips