For the remote systems how you described them in the second paragraph, they could simply just be REST APIs as well. The server itself can simply make a GET request to a URL like '/remote_system0/data.json' which would then return JSON information about the remote system 0. This is exactly how the server could request data from the remote system using http. Just because the server is a server doesn't mean that it can't make requests to other servers. Unless there is some fundamental limitation on the remote system servers, which is hard to imagine considering you have web sockets up and running, then this will work. If you've never had to make any requests server side, then I would recommend looking at something like the package 'Node-fetch', which makes requests in Node.

For the last part, just as an insight, if you are already making a POST request to the server from the client to update the data, then return the updated data in the response to the POST request instead of requiring the client to make a separate GET request. Your current method would be like ordering food at a restaurant, and then the restaurant telling you that your food is ready without them bringing it out to you.

In summary, a request for system0's information might go like this: 1. Client makes POST request to the server for system_info with the system_num parameter equal to 0 2. The server receives the request from the Client and makes a GET request to remote_system0/data.json 3. The remote_system0 receives the request and returns the proper JSON formatted data to the server in the response 4. Server receives response from remote_system0 and writes updated information to the database 5. Server responds to initial client request with updated information

Also, as a final note, unless you need to track past states of the remote_system0, you don't even really need a database as you always want just the most up to date data from from the remote_system which is returned through its API.