In case of we have proper security groups and private/public subnets,
is there any security benefit on separating AWS private subnet?
For example, I have 1 ELB(public subnet) and 2 EC2(Frontend and Backend in the same private subnet).
ELB -> Frontend -> Backend network security is properly secured by security groups.
At this point, is there any security advantage on separating subnets between Frontend and Backend?
Before: ELB(Public subnet) -> EC2(Frontend, Private subnet A) -> EC2(Backend, Private subnet A)
After: ELB(Public subnet) -> EC2(Frontend, Private subnet A) -> EC2(Backend, Private subnet B)