load repeater contents asynchronously

You need to enable caching.

I suggest you do Output cache (full page) that caches the full HTML output of pages, but you may go with Partial output cache that caches the HTML output of individual page components (web parts).

• Caching page output
• Partial output cache

hello Peter, well actually the cache concept is different from what I want in my page, I want to divide the page loading between immediate and synchronous (for light data like texts and titles) and asynchronous data like repeaters that contain heavy data (videos, images..), is this option can be achieved with kentico?

I don't think that there is anything "out of the box" you will probably end up creating you own "ansync repeater web part". Check the market place there is smart search results. it shows smart search result asynchronously, I guess you might borrow some ideas from there.

thank you peter, but generally speaking, besides chache, what do you do if you had a heavy loading repeater, that caused a slow page display? Because actually I am not considering building a repeater, I think it has to have another turn around solution.

I generally prefer not to use repeater. I'd rather create a custom search index. It works much much faster then repeater and there is no DB connection in this case you operate with local files on disc on the exact same server. Try it. It might give you a much better performance and you don't have to develop a custom web part. P.S. you might even use that custom smart search web part that I mentioned above.

The webpart at https://devnet.kentico.com/marketplace/web-parts/seo-friendly-infinite-scroll-lazy-load-repeater will load repeater contents async