Local Secondary Index (LSI) concept in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the purpose of Local Secondary Index (LSI)

What is the main purpose of a Local Secondary Index (LSI) in DynamoDB?

A To replicate data across multiple regions automatically

B To create a global index that spans all partitions with a different partition key

C To allow querying data using an alternate sort key while keeping the same partition key

D To increase the write throughput capacity of the table

💡 Hint

Think about how LSI relates to the partition key and sort key in DynamoDB.

An LSI lets you query the table using the same partition key but a different sort key, enabling more flexible queries without duplicating data.

❓ query_result

intermediate

Query result using LSI with alternate sort key

Given a DynamoDB table with partition key UserID and sort key Timestamp, and an LSI with the same partition key UserID but alternate sort key OrderStatus, what will the following query return?

Query on LSI where UserID = '123' and OrderStatus = 'Pending'

A No items because LSI cannot be queried

B All items with UserID '123' regardless of OrderStatus

C All items with OrderStatus 'Pending' regardless of UserID

D All items with UserID '123' and OrderStatus 'Pending'

💡 Hint

Remember that LSI uses the same partition key but a different sort key.

The query on the LSI filters items by the same partition key and the alternate sort key, returning only matching items.

📝 Syntax

advanced

Identify the correct syntax to create an LSI

Which of the following JSON snippets correctly defines a Local Secondary Index (LSI) when creating a DynamoDB table?

A { "IndexName": "StatusIndex", "KeySchema": [{"AttributeName": "UserID", "KeyType": "HASH"}, {"AttributeName": "OrderStatus", "KeyType": "RANGE"}], "Projection": {"ProjectionType": "ALL"} }

B { "IndexName": "StatusIndex", "KeySchema": [{"AttributeName": "OrderStatus", "KeyType": "HASH"}, {"AttributeName": "UserID", "KeyType": "RANGE"}], "Projection": {"ProjectionType": "ALL"} }

C { "IndexName": "StatusIndex", "KeySchema": [{"AttributeName": "UserID", "KeyType": "HASH"}], "Projection": {"ProjectionType": "ALL"} }

D { "IndexName": "StatusIndex", "KeySchema": [{"AttributeName": "OrderStatus", "KeyType": "RANGE"}], "Projection": {"ProjectionType": "ALL"} }

💡 Hint

LSI must use the same partition key as the base table and a different sort key.

Option A correctly defines an LSI with the same partition key UserID and a different sort key OrderStatus. Other options either swap keys or miss the partition key.

❓ optimization

advanced

Choosing LSI for query performance optimization

You have a DynamoDB table with a partition key CustomerID and sort key OrderDate. You want to efficiently query all orders by CustomerID filtered by OrderStatus. Which approach optimizes query performance?

A Create a Local Secondary Index with partition key <code>CustomerID</code> and sort key <code>OrderStatus</code>

B Create a Global Secondary Index with partition key <code>OrderStatus</code> and sort key <code>CustomerID</code>

C Scan the entire table and filter results by <code>OrderStatus</code>

D Add <code>OrderStatus</code> as a new attribute but do not index it

💡 Hint

Think about how LSI shares the partition key and allows alternate sort keys for efficient queries.

Using an LSI with the same partition key and alternate sort key OrderStatus allows efficient queries filtered by status without scanning the whole table.

🔧 Debug

expert

Diagnosing LSI write capacity error

You created a DynamoDB table with an LSI. When writing new items, you receive a ValidationException error stating: "The total size of indexed attributes exceeds the maximum allowed for LSI." What is the cause of this error?

A The combined size of the base table item and all indexed attributes for the LSI exceeds 10 GB limit

B The total size of all indexed attributes projected into the LSI exceeds 10 GB per partition key

C The total size of all indexed attributes projected into the LSI exceeds 10 MB per partition key

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💡 Hint

Check DynamoDB limits on LSI indexed attribute sizes per partition key.

DynamoDB limits the total size of all indexed attributes projected into an LSI to 10 GB per partition key. Exceeding this causes the error.