Wow. Nice post. This piece is an excellent example of expressing the complexities and thought processes that are are involved with designing a scaled/scalable network architecture using AWS. It is specific to their use case in some ways, but the author includes subsections that enumerate the pros and cons of the technical options that were considered at each stage of the design.

When I saw that their considerations included the possible use of a vpc transit gateway, I was hooked. (I was already aware of the service and its price point.. I consider TGW to be like the aws certificate manager service (for provisioning public certs): offered because there are users who are not burdened by a limited budget.) Heh. That did not necessarily remove it from consideration in this case. The author documents not only the high bandwidth charges involved with TGW use but also its technical limitations and why, along with the cost, why it is not a viable solution for their needs.

Anyways, for anyone interested in an excellent write-up of a non-trivial cloud networking environment, it is worth a 10-minute read.