Taking Advantage of Parallel Scans
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-query-scan.html
An application developer finds that a scan operation on a large DynamoDB table is taking a long time to execute. What can be used to decrease the execution time of the scan operation?

Answer options:

A.Use of parallel scans
B.Use of filter expression
C.Use of pagination
D.Use of projection expression

Answer: A
Option A is CORRECT because parallel scans can be used by multiple worker threads in an application to perform a scan of a DynamoDB table much faster.
Option B is incorrect because filter expression in a scan operation only filters the results. Scan operation still performs the same amount of read operations.
Option C is incorrect because pagination is used to separate the results of scan operation into “pages”.
Option D is incorrect because a projection expression is used to limit the attributes returned by the scan operation. It does not affect the speed of the scan operation.
Reference:
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Scan.html#Scan.ParallelScan