[nycphp-talk] So why is Ajax so fast?

Jon Baer jonbaer at
Fri Jan 12 11:04:45 EST 2007

This really depends on the library you are using and getting the  
server and XHR cache to work in sync w/ content-negotiated responses.

There is a bunch of stuff if you Google "XHR caching".  However I  
usually put this step in the "tuning" category when you are testing,  
there are a few testers out there (Selenium I think?) which will  
automate and give you a report.  The unit tests for these libraries  
usually have some details on what it's doing.

- Jon

On Jan 12, 2007, at 9:58 AM, Kenneth Downs wrote:

> We've all seen the amazing results you can get when you start using  
> Ajax, they all come down to one thing: speed.
> Question is, how is such a speed-up accomplished?  The standard  
> answer is that a complete trip to the server is averted, but this  
> is not true, in fact a complete cycle does occur:
> 1)  Request to server
> 2)  Possible db access on server
> 3)  rendering of HTML on server
> 4)  delivery to browser
> 5)  re-rendering of portions of screen
> Supposedly the js and css libraries are cached so we have not saved  
> the effort of retrieving them, this means the only thing we have  
> saved is the effort of re-rendering the screen from scratch.  To  
> put another way, we have not saved a whole lot of bytes of traffic,  
> or CPU cycles on the server.  The only thing that seems to be  
> missing is the render-from-scratch on the browser.
> Is this correct?  And if so, why is it so dramatically expensive to  
> render a page from scratch, that Ajax could make such a dramatic  
> improvement to the situation?
> <ken.vcf>
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