AWS Certified Database – Specialty — Question 266

A retail company uses Amazon Redshift for its 1 PB data warehouse. Several analytical workloads run on a Redshift cluster. The tables within the cluster have grown rapidly. End users are reporting poor performance of daily reports that run on the transaction fact tables.

A database specialist must change the design of the tables to improve the reporting performance. All the changes must be applied dynamically. The changes must have the least possible impact on users and must optimize the overall table size.

Which solution will meet these requirements?

Answer options

• A. Use the STL_SCAN view to understand how the tables are getting scanned. Identify the columns that are used in filter and group by conditions. Create a temporary table with the identified columns as sort keys and compression as Zstandard (ZSTD) by copying the data from the original table. Drop the original table. Give the temporary table the same name that the original table had.
• B. Run an explain plan to analyze the queries on the tables. Consider recommendations from Amazon Redshift Advisor. Identify the columns that are used in filter and group by conditions. Convert the recommended columns from Redshift Advisor into sort keys with compression encoding set to RAW. Set the rest of the column compression encoding to AZ64.
• C. Run an explain plan to analyze the queries on the tables. Consider recommendations from Amazon Redshift Advisor. Identify the columns that are used in filter and group by conditions. Convert the recommended columns from Redshift Advisor into sort keys with compression encoding set to LZO. Set the rest of the column compression encoding to Zstandard (ZSTD).
• D. Run an explain plan to analyze the queries on the tables. Consider recommendations from Amazon Redshift Advisor. Identify the columns that are used in filter and group by conditions. Create a deep copy of the table with the identified columns as sort keys and compression for all columns as Zstandard (ZSTD) by using a bulk insert. Drop the original table. Give the copy table the same name that the original table had.

Correct answer: B

Explanation

Amazon Redshift Advisor provides automated recommendations for optimizing sort keys. For optimal query performance, the primary sort key column should be configured with RAW compression to prevent decompression overhead during range scans, while other columns should use AZ64 compression to achieve high data compression and fast query execution. Modifying the table properties dynamically using ALTER TABLE commands avoids the need for disruptive deep copies, which minimizes the impact on active users.