Index projection types (ALL, KEYS_ONLY, INCLUDE) in DynamoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What does the KEYS_ONLY projection type include in a DynamoDB index?

In DynamoDB, when you create a secondary index with the KEYS_ONLY projection type, which attributes are included in the index?

A Only the non-key attributes specified explicitly

B All attributes from the base table

C Only the primary key attributes of the base table and the index key attributes

D All attributes except the primary key attributes

💡 Hint

Think about what minimal data is needed to uniquely identify items in the index.

The KEYS_ONLY projection type includes only the primary key attributes of the base table and the index key attributes. This keeps the index small and efficient.

❓ query_result

intermediate

Which projection type returns all attributes in a DynamoDB index query?

You query a DynamoDB secondary index with the projection type set to ALL. What attributes will the query return?

A All attributes from the base table item

B Only the primary key attributes of the base table

C Only the index key attributes

D Only the attributes explicitly included in the index

💡 Hint

ALL means everything is included.

The ALL projection type includes all attributes from the base table in the index, so queries return the full item.

📝 Syntax

advanced

Identify the correct syntax to specify an INCLUDE projection with attributes in a DynamoDB index creation.

Which of the following JSON snippets correctly defines an INCLUDE projection with attributes 'Name' and 'Age' for a DynamoDB secondary index?

A { "Projection": { "ProjectionType": "INCLUDE", "NonKeyAttributes": ["Name", "Age"] } }

B { "Projection": { "ProjectionType": "INCLUDE", "Attributes": ["Name", "Age"] } }

C { "ProjectionType": "INCLUDE", "NonKeyAttributes": ["Name", "Age"] }

D { "Projection": { "Type": "INCLUDE", "NonKeyAttributes": ["Name", "Age"] } }

💡 Hint

Check the exact property names required by DynamoDB for projections.

The correct syntax requires the 'Projection' object with 'ProjectionType' set to 'INCLUDE' and the 'NonKeyAttributes' array listing the attributes.

❓ optimization

advanced

Choosing the best projection type for a read-heavy application with frequent queries on a few attributes

You have a DynamoDB table with many attributes, but your application mostly queries a few specific attributes along with the keys. Which projection type should you choose for the secondary index to optimize read performance and storage?

A ALL, to have all attributes available for queries

B INCLUDE, specifying only the frequently queried non-key attributes

C No projection, use the base table for all queries

D KEYS_ONLY, to minimize index size and speed up queries

💡 Hint

Think about balancing storage size and query efficiency for specific attributes.

INCLUDE projection lets you specify only the needed non-key attributes, reducing index size and improving query speed for those attributes.

🔧 Debug

expert

Why does a query on a KEYS_ONLY projected index fail to return a non-key attribute?

You created a secondary index with KEYS_ONLY projection and query it expecting to get a non-key attribute 'Email'. The query returns no 'Email' attribute. Why?

A Because the query syntax is incorrect and does not request 'Email'

B Because the base table does not have the 'Email' attribute

C Because 'Email' is not a valid attribute name in DynamoDB

D Because KEYS_ONLY projection does not include non-key attributes like 'Email' in the index

💡 Hint

Recall what KEYS_ONLY projection includes in the index.

KEYS_ONLY projection includes only primary key attributes and index keys, so non-key attributes like 'Email' are not stored in the index and cannot be returned by queries on it.