Response time plays a key role in how users perceive your
application; nobody likes a slow application. By tracking your
application's usage and adjusting its performance, you can dramatically
improve the quality of your application's user experience.
There are two approaches to improving your application's
performance. First, you can improve the actual response time by optimizing
the application logic. Second, you can enhance the perceived performance
by adjusting the order in which you load resources.
The following guidelines discuss both approaches:
- Use YQL to
cache queries. Combine multiple queries into one call.
- Use unique URLs for resources such as images or media files.
When you update the content of a resource, you should update the URL
so that the cache is flushed with the updated content.
- Write modular code and reuse it as much as possible. Reuse is
especially important because Caja, the technology used by
Yahoo! to ensure the security of user data, can increase the size of
your JavaScript code by 2-3 times because it adds a series of checks
and verification steps.
- To improve perceived response time, defer loading resources
until your application has launched. Also, load resources after
fully rendering the page.
- Present a progress indicator while resources are being
loaded.
- Monitor the response time of your server. If your application
takes more than 9 seconds to load, YAP displays an error message to
the user. If an image request takes longer than 3 seconds, the
request is terminated and the image will not be available for your
application.
- Don't use multiple, sequential calls if they can be combined
into a single call.
- Don't overload your front-end with unnecessary JavaScript code
if the same functionality can be achieved in the back-end.
YAP caches images from third-party servers, usually for a day or
so. You can control this behavior by including the standard Cache-Control
header in your HTTP responses.