Do I need to use WebSocket here?

Question

AJAX

The site has a system for sending Ajax requests every 5 seconds - to display the latest purchases, will there be a big load if, say, 1000-4000 people visit the site per day?

Answer 1

SSE
If 1000-4000 people a day, then this is extremely small, at least anything will do here, it’s more important to look at how many people you have in your peak, i.e. simultaneously

Answer 2

Do not plant such a bomb at the start, then it is more difficult to redo it than to do it right now.
Server site event or websockets, for me it’s the same thing, but websockets are more universal (i.e. it’s convenient to use your own websocket server and backend for inter-process communication)