Is there a best practice to configure private VPC to access S3 bucket?

I created a VPC for my Elastic Beanstalk in China. The service delivers files from an S3 bucket located in the same region in China (cn-north-1). If the same service is running in the AWS Default VPC, I have access times of 1 to 2 seconds, but the same service in the VPC always takes 3 to 5 seconds. Do I have to pay attention to anything with the VPC?