You are uploading large files to AWS S3 bucket, ranging from 1GB – 3GB. Your organization has a requirement to calculate the hash checksum of the file by reading entire file so the users can validate the checksum to identify any potential corruptions during downloads. For this, you created a Lambda function and getting it triggered through S3 notifications. However, the request is getting timed out. What could be the reason?

Answer options:

A.Lambda function is configured with minimal memory of 128 MB.B.Lambda function is set to run in a private VPC without NAT Gateway or VPC Endpoint.
C.You have not setup S3 bucket name in the environment variable.
D.Lambda function is created in a different region than S3 bucket.

Answer: B
Option A is not correct. If the function reaches the maximum configured memory, in this case
128 MB, the function gets terminated with an error message as below, not as request timed out.
REPORT RequestId: xxxxxxxx Duration: xxxxx ms Billed Duration: xxxxx ms
Memory Size: 128 MB Max Memory Used: 129 MB RequestId: xxxxxxx Process exited before completing request
 Option B is correct. AWS Lambda functions can run within a private VPC with the resources allocated inside the subnet provided during configuration.
For the lambda function to access S3 service endpoint from within private VPC, there should be a NAT Gateway or S3 VPC Endpoint configured in the route table associated with the subnet which was chosen during Lambda function setup. If not, the request would get timed out.
https://aws.amazon.com/premiumsupport/knowledge-center/internet-access-lambda-function/
Option C is not correct. Bucket need not be configured as environment variable.
Lambda function environment variables are used to configure additional parameters that can be passed to lambda function.
https://docs.aws.amazon.com/lambda/latest/dg/env_variables.html
Option D is not correct. As long as Lambda function has internet access, it can access S3 service endpoints irrespective of S3 bucket region.