ECS and restful APIs

The game I am working on professionally utilises restful API web requests for the majority of client/server communication. I have been reading up on the ECS system and I understand about the importance of separating data and the systems that work on/with that data. I'm struggling to see where this type of communication would fit into the system.

Clearly the requests operate on data, and the responses would provide new data for the system but will this just involve deferring to standard C# code? What about plugins like BestHTTP, how much would (https://assetstore.unity.com/packages/tools/network/best-http-10872) that need to be modified to work with an ECS codebase?