Index capacity and cost in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an index in DynamoDB?

An index in DynamoDB is a data structure that improves the speed of data retrieval operations on a table by allowing queries on non-primary key attributes.

intermediate

How does a Global Secondary Index (GSI) affect capacity in DynamoDB?

A GSI consumes additional read and write capacity units because it maintains a copy of data with different key attributes, increasing the cost of operations.

intermediate

What is the difference in write capacity cost between a table and its Local Secondary Index (LSI)?

Writes to a table also consume write capacity units for its LSI because the index is updated synchronously, but LSIs do not consume separate read capacity units since they share the table's read capacity.

beginner

Why can adding too many indexes increase your DynamoDB costs?

Because each index requires additional storage and capacity units for writes and reads, more indexes mean more resources used, which increases your overall cost.

intermediate

How can you reduce the cost impact of indexes in DynamoDB?

You can reduce costs by limiting the number of indexes, choosing only necessary attributes to project, and using on-demand capacity mode to pay only for what you use.

Which type of index in DynamoDB requires separate read and write capacity units?

A Global Secondary Index (GSI)

B Local Secondary Index (LSI)

C Primary Key

D No index requires capacity units

Global Secondary Indexes consume separate read and write capacity units because they maintain a separate copy of data.

What happens to write capacity units when you write to a table with a Local Secondary Index?

A Write capacity units are consumed for both the table and the LSI

B Only the table consumes write capacity units

C Only the LSI consumes write capacity units

D No write capacity units are consumed

Writes to the table also consume write capacity units for the LSI because it updates synchronously.

Which of the following increases DynamoDB costs the most?

A Projecting only keys in indexes

B Using only the primary key

C Using on-demand capacity mode

D Adding multiple Global Secondary Indexes

Multiple GSIs increase costs because each requires additional capacity and storage.

How can you reduce read capacity costs for an index?

A Add more GSIs

B Project only necessary attributes

C Use larger read capacity units

D Avoid using indexes

Projecting only necessary attributes reduces the size of data read, lowering read capacity costs.

Which index type shares read capacity units with the base table?

A Primary Key

B Global Secondary Index (GSI)

C Local Secondary Index (LSI)

D None

LSIs share the table's read capacity units, unlike GSIs which have separate capacity.

Explain how Global Secondary Indexes affect DynamoDB capacity and cost.

Think about how GSIs duplicate data and require extra resources.

Describe strategies to manage and reduce the cost impact of indexes in DynamoDB.

Focus on minimizing resource use and paying only for what you need.