Parallel scan in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Understanding Parallel Scan Segments

You have a DynamoDB table with 1000 items. You perform a parallel scan with Segment=0 and TotalSegments=4. What portion of the table does this scan segment read?

A Approximately 25% of the table items

B All items in the table

C Only the first 100 items

D Only items with a specific partition key

💡 Hint

Think about how the total segments divide the table for parallel scanning.

When you set TotalSegments=4, the table is divided into 4 parts. Each segment scans roughly 1/4 of the table. So segment 0 scans about 25% of the items.

📝 Syntax

intermediate

Correct Syntax for Parallel Scan Parameters

Which of the following is the correct way to specify parameters for a parallel scan in DynamoDB using the AWS SDK?

A { TableName: 'MyTable', Segment: 4, TotalSegments: 1 }

B { TableName: 'MyTable', TotalSegments: 0, Segment: 4 }

C { TableName: 'MyTable', Segment: 1, TotalSegments: 4 }

D { TableName: 'MyTable', Segment: 0 }

💡 Hint

Remember that Segment must be less than TotalSegments.

The Segment parameter must be a number from 0 to TotalSegments - 1. Option C correctly sets Segment=1 and TotalSegments=4.

❓ optimization

advanced

Optimizing Parallel Scan Performance

You want to speed up scanning a large DynamoDB table using parallel scan. Which approach will most effectively improve scan speed?

A Use a single scan without segments to avoid overhead

B Scan only the first 100 items repeatedly

C Set <code>Segment</code> to a value larger than <code>TotalSegments</code>

D Increase <code>TotalSegments</code> to a higher number and run scans concurrently

💡 Hint

Think about how dividing work among multiple workers helps.

Increasing TotalSegments allows more parallel workers to scan different parts of the table simultaneously, improving speed.

🔧 Debug

advanced

Identifying Error in Parallel Scan Parameters

You run a parallel scan with parameters: { TableName: 'MyTable', Segment: 5, TotalSegments: 4 }. What error will this cause?

A ResourceNotFoundException: Table does not exist

B ValidationException: Segment must be less than TotalSegments

C No error, scan runs normally

D ProvisionedThroughputExceededException

💡 Hint

Check the allowed range for the Segment parameter.

The Segment value must be between 0 and TotalSegments - 1. Here, 5 is not less than 4, so a validation error occurs.

🧠 Conceptual

expert

Effect of Parallel Scan on Read Capacity Units (RCUs)

You perform a parallel scan on a large DynamoDB table with TotalSegments=10. How does this affect the consumption of read capacity units compared to a single scan?

A Total RCUs consumed is roughly the same, but spread across 10 concurrent workers

B Total RCUs consumed is 10 times higher than a single scan

C Total RCUs consumed is 1/10th of a single scan

D Parallel scan does not consume any RCUs

💡 Hint

Think about how parallel scan divides the work but still reads the entire table.

Parallel scan divides the table into segments scanned concurrently. The total read capacity units consumed is about the same as a full scan, but the load is distributed across multiple workers.