DynamoDB - with Serverless
You want a Lambda function to update a user's email in DynamoDB only if the user exists. Which approach correctly ensures this conditional update?
You want a Lambda function to update a user's email in DynamoDB only if the user exists. Which approach correctly ensures this conditional update?
hard🚀 Application Q15 of 15
Step-by-Step Solution
Solution:
Step 1: Understand conditional update in DynamoDB
To update only if an item exists, use ConditionExpression with 'attribute_exists' on the key.Step 2: Apply ConditionExpression in update method
docClient.update supports ConditionExpression to prevent overwriting non-existing items.Step 3: Evaluate other options
Using put without condition overwrites or creates new items; delete before update is inefficient; get then put is not atomic.Final Answer:
Use docClient.update with ConditionExpression 'attribute_exists(id)' -> Option CQuick Check:
Conditional update = update + attribute_exists [OK]
Quick Trick: Use ConditionExpression 'attribute_exists' for safe updates [OK]
Common Mistakes:
MISTAKES- Using put which overwrites without condition
- Deleting item before update unnecessarily
- Not using atomic conditional update
Master "with Serverless" in DynamoDB
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