Scan vs query performance in AWS - Quick Revision & Key Differences

Recall & Review

beginner

What is a Scan operation in AWS DynamoDB?

A Scan operation reads every item in a table to find matching data. It checks all items, which can be slow and costly for large tables.

beginner

What is a Query operation in AWS DynamoDB?

A Query operation finds items by searching only a specific partition key and optional sort key. It is faster and more efficient than Scan.

beginner

Why is Query generally faster than Scan in DynamoDB?

Query targets specific partitions using keys, so it reads fewer items. Scan reads the whole table, which takes more time and resources.

intermediate

When might you use Scan instead of Query?

Use Scan when you need to read all items or when you don't know the partition key. But expect slower performance and higher cost.

intermediate

How can you improve Scan performance in DynamoDB?

You can use filters to reduce returned data, parallel scans to read faster, and limit the number of items scanned per request.

Which DynamoDB operation reads the entire table to find matching items?

A Query

B Scan

C GetItem

D UpdateItem

Scan reads every item in the table, while Query targets specific keys.

Which operation is more efficient when you know the partition key?

A Scan

B DeleteItem

C BatchWrite

D Query

Query uses the partition key to quickly find items, making it more efficient.

What is a downside of using Scan on large DynamoDB tables?

A It consumes more read capacity and time

B It reads only one item

C It is very fast

D It updates items automatically

Scan reads all items, which uses more capacity and takes longer.

How can you reduce the amount of data returned by a Scan?

A Use filters

B Use Query instead

C Use GetItem

D Use UpdateItem

Filters limit the data returned after scanning all items.

Which method can speed up Scan operations by dividing the work?

A Batch Write

B Query

C Parallel Scan

D GetItem

Parallel Scan splits the table into segments scanned simultaneously.

Explain the main differences between Scan and Query operations in DynamoDB and their impact on performance.

Think about how much data each operation reads.

Describe scenarios when you would choose Scan over Query in DynamoDB and how to optimize Scan performance.

Consider cases where you need all data or no key is available.