In addition to the three partitions (global, china and us gov) documented at https://docs.aws.amazon.com/general/latest/gr/aws-arns-and-n... AWS sdks include two additional partitions: us-iso and us-iso-b, which have endpoints in the "c2s.ic.gov" and "sc2s.sgov.gov" dns hierarchy, respectively.

Reposted with a clearer title from https://news.ycombinator.com/item?id=23297872 with permission.