A developer is working on an app for a company that uses an Amazon DynamoDB...

Requirement Summary:

DynamoDB table Orders

Partition key: OrderID

No sort key

100,000+ records

Need toefficiently retrieveall records where:

OrderSource = "MobileApp"

Mustoptimize for user experience(i.e., performance)

Evaluate Options:

Option A: Scan with FilterExpression

❌Inefficientfor large tables

AScanreadsevery itemin the table and then applies a filter condition.

This isslow, expensive, andnot scalableas the dataset grows.

Option B: Create a Local Secondary Index (LSI) with OrderSource

❌Invalid: LSIs require thesame partition key(OrderID) as the base table.

Since OrderSource is not part of the primary key, and we want to querybased on it, LSI won’t help.

Option C: Create a GSI with OrderSource as the sort key

❌Misuse of sort key: Querying bysort key alone is not allowedin DynamoDB.

Youmust specify a partition keyin a Query.

This design is not valid for the use case.

Option D: Create a GSI with OrderSource as the partition key

✅✅BEST CHOICE: With a GSI on OrderSource, you canquery efficientlyfor all items where OrderSource = "MobileApp".

DynamoDB GSIs allow analternative access patternfor queries not supported by the base table schema.

GSI Design:https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GSI.html

Querying a GSI:https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.html

Scan vs Query:https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-query-scan.html