Exam AWS Certified Database - Specialty topic 1 question 318 discussion

A,C query faster then scan

AD The daily report generator computes the "sum totals" of the attributes. In order to do this, you have to go over all the items (scan) and not query some of them.

Cannot query the index as you need to provide the partition key, and the use case needs to scan all items. The index will help because it will serve as a sparse index (only items with attribute) and at the same time having only two attributes reduces the size, thus also the size that the scan needs.

https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-query-scan.html

A: By creating a GSI with the appropriate partition and sort keys, the report generator can efficiently query the index for the required attributes, minimizing the time required for calculations. D: It need to sum all the items with the dimension attribute, which means all items will be retrieved in the GSI table. So scan will be better than query.

I Think AC

Scan runs on table Query runs on index

B: No. An LSI is an index that is only spread across the same partition as the table, which can improve read performance for queries that scan a small number of items. In this case, the LSI will be scanned to compute the sum totals of the two attributes, so it is not as effective as creating a GSI. D: No, because scanning an index is not as efficient as querying an index. E: No, because the BatchGetItem operation is used to get multiple items from a table or index. The report generator only needs to get one item from the index, so the BatchGetItem operation would be overkill. https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/SecondaryIndexes.html https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.html https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/API_BatchGetItem.html

https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LSI.html

The Answer: BE

By creating a GSI with the appropriate partition and sort keys, the report generator can efficiently query the index for the required attributes, minimizing the time required for calculations. Additionally, using the BatchGetItem operation allows the report generator to retrieve multiple items in a single request, further reducing the processing time. Therefore, the combination of steps A and E would help minimize the time taken for report generation in this scenario.