What is the default region for all AWS SDKs?

The default region for all AWS SDKs is indeed us-east-1. This region, located in Northern Virginia, is often referred to as the "default" region because it serves as the initial point of contact for many AWS API calls when no specific region is specified by the user. The significance of having a default region is to standardize the endpoint that SDKs will connect to, simplifying the initialization process for developers who may not explicitly set a region in their application configurations.

When using an AWS SDK without setting a different region, your API requests will route through the us-east-1 region, ensuring that resources can be accessed and utilized even without user intervention. This can impact application design choices, especially concerning latency, availability, and compliance with data residency regulations, since users might want to operate in a region closer to their location or their customers.

Other regions listed are valid AWS regions, but they are not the default set in AWS SDKs. This emphasizes the importance of understanding AWS's regional services and how defaults can affect service deployment and user experience.