AWS Lambda Not Writing to DynamoDB After S3 Upload Trigger

Based on the information provided, there are a few potential reasons why your Lambda function might not be writing to DynamoDB after an S3 upload trigger. Here are some troubleshooting steps and considerations:

1. Verify S3 Trigger Configuration: Ensure that the S3 trigger is correctly set up for your Lambda function. Check that the event type "All object create events" is properly configured and that the bucket name (lambda-bucket9989) is correct.

2. Check Lambda Function Execution: Verify that your Lambda function is actually being triggered when you upload a file to S3. You can do this by checking the CloudWatch Logs for your Lambda function. If there are no logs, it might indicate that the function is not being invoked.

3. Review Lambda Function Code: Make sure your Lambda function code is correctly retrieving the S3 object metadata and attempting to write to DynamoDB. Double-check that you're using the correct DynamoDB table name ("newtable") and partition key ("unique") in your code.

4. Examine Lambda Function Permissions: While you mentioned that the IAM role has full DynamoDB access, it's worth double-checking that the role also has the necessary permissions to read from S3. The function needs to be able to get objects from the S3 bucket to retrieve metadata.

5. Increase Lambda Timeout and Memory: You mentioned increasing the timeout, which is good. If your function is processing large files or performing complex operations, you might also need to increase the allocated memory.

6. Handle Exceptions in Lambda Code: Ensure that your Lambda function code includes proper error handling. If an exception occurs during execution, it should be logged to CloudWatch Logs. This can provide valuable information for debugging.

7. Check DynamoDB Write Capacity: Verify that your DynamoDB table has sufficient write capacity. If the table is using provisioned capacity and all write capacity units are consumed, writes may fail.

8. Test Lambda Function Independently: Try invoking your Lambda function directly (not through the S3 trigger) with a test event that mimics an S3 upload. This can help isolate whether the issue is with the S3 trigger or the Lambda function itself.

9. Monitor CloudWatch Metrics: Check CloudWatch metrics for your Lambda function, S3 bucket, and DynamoDB table. Look for any unusual patterns or error indicators.

10. Use AWS X-Ray: Consider enabling AWS X-Ray for your Lambda function to get more detailed tracing information. This can help identify where the function might be failing or experiencing delays.

If after checking these items you're still experiencing issues, you may want to share your Lambda function code (with sensitive information redacted) for further assistance. Additionally, any error messages or logs you can provide would be helpful in diagnosing the problem.

Remember to always test your changes in a non-production environment first, and make sure to follow AWS best practices for security and resource management.

Sources
Tutorial: Using an Amazon S3 trigger to invoke a Lambda function - AWS Lambda
Invoke a Lambda function from an Amazon S3 trigger - AWS Lambda
Invoke a Lambda function from a DynamoDB trigger - AWS Lambda

Hello,

You can check Lambda logs on console, which is in cloudwatch logs, you could find errors in log. Also you can test your function, first with a dummy event, and then using the trigger, for example: https://docs.aws.amazon.com/lambda/latest/dg/with-s3-example.html

Is your lambda function in the same region as the s3 bucket?