Pagination with SDK in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Understanding DynamoDB SDK Pagination Output

You run a DynamoDB query using the AWS SDK with a limit of 2 items per page. The table has 5 items matching the query. What will the LastEvaluatedKey value be after the first page is fetched?

DynamoDB

const params = { TableName: 'Products', KeyConditionExpression: 'Category = :cat', ExpressionAttributeValues: { ':cat': 'Books' }, Limit: 2 };
const data = await dynamodb.query(params).promise();
console.log(data.LastEvaluatedKey);

A The primary key of the last item in the first page (second item)

B The primary key of the second item in the result set

C null (no more pages)

D The primary key of the last item in the entire table

💡 Hint

Think about what LastEvaluatedKey represents in pagination.

LastEvaluatedKey is the key of the last item returned in the current page. It is used to fetch the next page starting after this item.

📝 Syntax

intermediate

Correct SDK Parameter for Pagination

Which of the following is the correct way to specify the starting point for the next page in a DynamoDB query using the AWS SDK?

A ExclusiveStartKey: lastEvaluatedKey

B StartKey: lastEvaluatedKey

C LastKey: lastEvaluatedKey

D NextKey: lastEvaluatedKey

💡 Hint

Check the official AWS SDK documentation for the exact parameter name.

The correct parameter to continue a query from a specific point is ExclusiveStartKey.

❓ optimization

advanced

Optimizing Pagination for Large Result Sets

You want to fetch all items matching a query but avoid loading too many items into memory at once. Which approach is best when using DynamoDB SDK pagination?

A Use Scan instead of Query to get all items faster

B Set Limit to a very large number to get all items in one request

C Set a small Limit and use ExclusiveStartKey to fetch pages one by one in a loop

D Fetch all pages in parallel using multiple queries with different ExclusiveStartKeys

💡 Hint

Think about memory usage and API limits.

Using a small Limit and paginating with ExclusiveStartKey avoids loading too many items at once and respects DynamoDB limits.

🔧 Debug

advanced

Why Does Pagination Stop Early?

You use the DynamoDB SDK to paginate through query results with Limit=3. After fetching the first page, LastEvaluatedKey is null, but you know more items exist. What is the likely cause?

A The table has only 3 items matching the query

B Limit parameter is ignored by DynamoDB

C You forgot to set ExclusiveStartKey for the second page

D The query filter excludes remaining items after the first page

💡 Hint

Consider how filters affect the result count.

Filters are applied after fetching items, so if many items are filtered out, fewer results are returned and pagination may stop early.

🧠 Conceptual

expert

Understanding Pagination Consistency in DynamoDB

When paginating query results in DynamoDB, which statement about consistency is true?

A Each page reflects a consistent snapshot of the data at the query start time

B Pages may reflect different data if items are added or deleted during pagination

C Pagination guarantees strongly consistent reads across all pages by default

D Pagination disables eventual consistency for the query

💡 Hint

Think about how DynamoDB handles eventual consistency and pagination.

DynamoDB queries are eventually consistent by default, so data can change between pages if items are added or deleted.