Funnily enough I was just discussing this in a seemingly unrelated thread:
Cloudfront is one of the largest CDNs on the internet so it’s not a surprise that the PSL service is hosted there, although there’s certainly no guarantee it will remain that way. Nor is there a guarantee that it is the PSL that your KeePass instance is trying to connect to - you’d have to dig into more details in a network and/or process monitoring tool to prove this or look through the source code to verify where the plugin connects to.
Essentially, KeePassRPC will not work very well without access to the internet, but it will still function to a degree, and in a way that ensures the fallback behaviour is stricter so no security or privacy problems are introduced if it is unable to connect to the internet for any reason.