Which solution will improve this lag time the MOST?
In each of the two new Regions, set up the Lambda functions to run in a VPC. Set up an S3 gateway endpoint in that VPC.
Turn on S3 Transfer Acceleration on the S3 bucket in eu-north-1. Change the application to use the new S3 accelerated endpoint when the application uploads data to the S3 bucket.
Create an S3 bucket in each of the two new Regions. Set the application in each new Region to upload to its respective S3 bucket. Set up S3 Cross-Region Replication to replicate data to the S3 bucket in eu-north-1.
Increase the memory requirements of the Lambda functions to ensure that they have multiple cores available. Use the multipart upload feature when the application uploads data to Amazon S3 from Lambda.
Explanations:
Using an S3 gateway endpoint in a VPC would optimize network traffic within the region, but it does not address the cross-region lag of transferring data to S3.
S3 Transfer Acceleration improves upload speed over long distances but doesn’t significantly reduce the lag caused by cross-region data flow to a central bucket.
Creating S3 buckets in each region and using Cross-Region Replication will reduce lag by replicating data from the new regions to the central bucket in eu-north-1.
Increasing Lambda memory or using multipart uploads may improve processing speed, but it won’t reduce cross-region data transfer lag to the S3 bucket.
To the best of my knowledge, the answer is:
Create an S3 bucket in each of the two new Regions. Set the application in each new Region to upload to its respective S3 bucket. Set up S3 Cross-Region Replication to replicate data to the S3 bucket in eu-north-1.