I have a project with two AWS servers, one in China and one in Singapore. I built custom APIs to allow them to communicate with each other, which was working fine for months. Then this morning, without any changes to the code, they stopped working. The Singapore server threw a 500 error trying to connect to the China server, and the China server threw a "Connection timed out" error. I can access both servers independently, there's nothing wrong with EC2 or RDS or anything that I can see.
Could this be the Chinese internet firewall filtering or blocking my servers, or am I being paranoid? Is this something that can be fixed with nginx conf or am I totally screwed? Please help!