You want to update a user's email in DynamoDB only if the user exists. Which operation and condition should you use?

hard📝 Best Practice Q15 of 15

AWS - DynamoDB

AUse <code>query</code> to find the user, then <code>put</code> to update

BUse <code>get</code> to check existence, then <code>put</code> to update

CUse <code>put</code> without any condition

DUse <code>put</code> with a condition expression checking attribute_exists(userId)

Step-by-Step Solution

Solution:

Step 1: Understand conditional update
To update only if the user exists, use put with a condition expression that checks for the user's existence.
Step 2: Use attribute_exists condition
The condition attribute_exists(userId) ensures the item exists before updating, preventing overwriting non-existing items.
Final Answer:
Use put with a condition expression checking attribute_exists(userId) -> Option D
Quick Check:
Conditional put prevents overwriting missing items [OK]

Quick Trick: Use put with condition attribute_exists() to update safely [OK]

Common Mistakes:

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