what technique can be used to minimize the impact of a …

A.Set a smaller page size for the scan

A

Reference:
http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/QueryAndScanGuidelines.html

Instead of using a large Scan operation, you can use the following techniques to minimize the impact of a scan on a table’s provisioned throughput.

Reduce Page Size

Because a Scan operation reads an entire page (by default, 1 MB), you can reduce the impact of the scan operation by setting a smaller page size. The Scan operation provides a Limit parameter that you can use to set the page size for your request. Each Scan or Query request that has a smaller page size uses fewer read operations and creates a “pause” between each request. For example, if each item is 4 KB and you set the page size to 40 items, then a Query request would consume only 40 strongly consistent read operations or 20 eventually consistent read operations. A larger number of smaller Scan or Query operations would allow your other critical requests to succeed without throttling.

Isolate Scan Operations

DynamoDB is designed for easy scalability. As a result, an application can create tables for distinct purposes, possibly even duplicating content across several tables. You want to perform scans on a table that is not taking “mission-critical” traffic. Some applications handle this load by rotating traffic hourly between two tables – one for critical traffic, and one for bookkeeping. Other applications can do this by performing every write on two tables: a “mission-critical” table, and a “shadow” table.