[jkarneges]

WebSockets are superior from a technical perspective, no arguing that. But, long-polling makes for more straightforward APIs, which could be valuable if you're more concerned about developer UX than the number of bytes on the wire.

For example, long-polling can actually be RESTful, so it fits in well with conventional API practices. It's also naturally resilient to network issues since each re-poll heals the stream. Users are very unlikely to lose data due to forgetting about some corner case.

[RyanZAG]

Websockets can be RESTful too. I've seen the following:

  GET /orders - fetch all orders
  GET /orders Upgrade: websocket - streaming view of all new orders

The problem with this type of RESTful integration though is the connection limit imposed by browsers. Of course, long poll has the identical problem. You can't long poll more than a couple endpoints.

[jkarneges]

True, you can use URI paths with WebSockets which at least makes the streams resource-oriented. CBIX does it: https://www.cbix.ca/api-websocket

I think calling this RESTful is a bit of a stretch though, at least in any conventional sense of what that means to people.