Limit and pagination in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this DynamoDB scan with Limit?

Consider a DynamoDB table named Books with 10 items. You run this scan command with Limit=3:

aws dynamodb scan --table-name Books --limit 3

What will be the number of items returned in Items?

A 10 items

B 3 items

C 0 items

D All items except 3

💡 Hint

The Limit parameter controls how many items are returned in one response.

The Limit=3 means the scan will return at most 3 items in the response, even if the table has more items.

❓ query_result

intermediate

What happens when you use LastEvaluatedKey in DynamoDB pagination?

You perform a scan on a DynamoDB table with Limit=2. The response includes LastEvaluatedKey. What does this key represent?

A The key to start the next scan to get more items

B The last item returned in the current scan

C The primary key of the first item in the table

D An error indicator for the scan

💡 Hint

Think about how you get the next page of results in DynamoDB.

LastEvaluatedKey is used as the ExclusiveStartKey in the next scan to continue from where the last scan stopped.

📝 Syntax

advanced

Which DynamoDB scan command correctly paginates to get the next 5 items?

You have the LastEvaluatedKey from a previous scan stored in a JSON file lastkey.json. Which command correctly uses it to get the next 5 items?

A aws dynamodb scan --table-name Books --limit 5 --last-evaluated-key file://lastkey.json

B aws dynamodb scan --table-name Books --limit 5 --start-key file://lastkey.json

C aws dynamodb scan --table-name Books --limit 5 --exclusive-start-key file://lastkey.json

D aws dynamodb scan --table-name Books --limit 5 --startExclusiveKey file://lastkey.json

💡 Hint

Check the exact parameter name for starting a scan from a key.

The correct parameter is --exclusive-start-key to specify where to continue scanning.

🧠 Conceptual

advanced

Why might a DynamoDB scan with Limit not return the exact number of items requested?

You set Limit=5 in a scan, but the response returns fewer than 5 items without LastEvaluatedKey. Why?

A Because Limit only applies to the number of attributes, not items

B Because Limit is ignored if the table has more items

C Because the scan failed and returned partial data

D Because the scan reached the end of the table and fewer items remain

💡 Hint

Think about what happens when you reach the last items in the table.

If fewer than the Limit number of items remain, the scan returns only those items and no LastEvaluatedKey.

❓ optimization

expert

How to efficiently paginate large DynamoDB tables without scanning all items?

You want to paginate through a large DynamoDB table efficiently. Which approach is best?

A Use Query with a partition key and ExclusiveStartKey for pagination

B Use Scan with Limit and LastEvaluatedKey repeatedly

C Use Scan without Limit to get all items at once

D Use Query without specifying a key to get all items

💡 Hint

Consider how DynamoDB is optimized for queries on keys.

Query with a partition key is efficient and supports pagination with ExclusiveStartKey. Scan reads the whole table and is slower.