Without requiring knowledge of the underlying infrastructure -> AWS Elastic Beanstalk.
S3, private, premier, subscription -> pre-signed URL for S3 when download.
accurate rolling average -> You need to store then re-read to calculate -> ElasticRedis, not durable(persistent), data can be lost.
AWS DynamoDB, LSI(Local Secondary Index), GSI(Glabal Secondary Index) -> LSI share partitionKey with the base table, it can have only the same partitionKey and multiple sortKey; GSI doesn't, it can have multiple partitionKey and multiple sortKey.
Low-latency, real time, highly-scalable, store in database -> AWS DynamoDB.
Used for outbound internet access from private subnets -> NAT gateway.
AWS CLI create-stack-set -> AWS CloudFormation StackSetss, create, update of delete Stacks across multiple accounts and regions with a single cloud formation template.