> Keep in mind that 150ms round-trip latency means at least 600ms latency when opening a webpage because of the TCP and TLS handshake.
The solution there is use a CDN, even for the API. Or some anycast IP solution like Global Accelerator (AWS), Global load balancer (GCP) or Front Door (Azure).
You connect to the nearest region for HTTPS handshake and then that takes the "fastest" route back to your origin.
There's a video from AWS documenting how Slack did exactly that: youtube.com/watch?v=oVaTiRl9-v0