Do you mean that loading your whole set of event data is very slow? If there are a very great many events, then bandwidth may be a problem, but there would have to be very many events for that. Perhaps your server is not performing very well?
Or do you mean that once all the data is loaded, there is another delay while rendering. The two phases are very separate.
The load fetch is about 300ms, but the render is about 6 secondes (not a server problem).
To display recurring events on agenda correctly, my fetch request constuct all single event over a year (for each recurring event).