Hello starterKapok
Welcome to microsoft Q&A,Thankyou for posting your query here.
Deploying an additional application server in Azure China and considering these optimizations, you should be able to improve the access latency for your Mainland China
Check if the Azure services you are using are available in both Azure China and Azure HK
Consider the network latency between Azure China and Azure HK. Although both regions are located in Asia, there may still be some network latency between them
Use tools like SockPerf to test the network latency between the two regions.
Establish an ExpressRoute connection between your Azure China and Azure HK regions.
Consider the data transfer cost between Azure China and Azure HK. Data transfer between regions can incur additional costs, so you need to make sure that the cost is within your budget.
Configure Azure Traffic Manager to route users to the appropriate application server based on their geographic location.
Configure Azure CDN to serve static assets from edge locations closer to users in Mainland China.
Hope this helps you.