Choosing the right location
Applications in App Engine are deployed regionally. This means that the infrastructure that's used to host it is spread across the zones within this region for high availability. The main consideration when it comes to choosing the region is where your end users will be connecting from. However, you should also remember that your app might use other GCP resources. This has an impact on delays as well as costs. Consult the documentation to see which regions the App Engine service is available in as this might change.
Important Note
Once the application has been deployed, you cannot change its region.