Amazon DocumentDB is a fast, scalable, highly available, and fully managed document database service that supports MongoDB workloads. You can use the same MongoDB application code, drivers, and tools that you do today to run, manage, and scale workloads on Amazon DocumentDB and enjoy improved performance, scalability, and availability without having to worry about managing the underlying infrastructure.
You can use Amazon DocumentDB in the following AWS regions: US East (N. Virginia, Ohio), US West (Oregon), Europe (Ireland, Frankfurt), and Asia Pacific (Tokyo, Seoul). For more information on AWS regions and services, please visit the AWS global region table.
from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/05/amazon-documentdb-available-in-asia-pacific-tokyo-and-seoul-regions-with-r5-instances/