Make Fewer and Smaller HTTP Requests
Making fewer HTTP requests that return less content is the single most effective technique for improving front-end performance. Each HTTP request usually takes at least 10 milliseconds to send and more time to return the page. Reducing the number of HTTP requests you make is often one of the most effective ways to improve site performance.
Reduce the Size and Number of Cookies
Cookies are always sent with each request for the same host or domain, so reduce the size and number of cookies to make requests quicker.
Reduce the Number of Images
If you have many small icons, make them one image or use CSS sprites, which require only one HTTP request. Header information, corners, button, or background images can be transferred using one or two CSS sprites. The exception to this is extremely large images, which can take more time to transfer.
This approach improves performance because instead of sending 10 requests for 1 KB each, you can send one request for 10 KB. In the first case, the minimum amount of time to load the page is 100 ms and the second, it's 10 ms. Also, using compression (gif, jpg), the single file compressed can be smaller than 10 files compressed, further saving loading time.
Consider Hidden Requests Carefully
Be aware of hidden requests, such as using
@import statements in CSS files. The
@import statement is a client-side statement, so each
import adds another request to the request for the main file.
You can generate more requests through calls to JavaScript. For example, if you include Omniture or Google Analytics, the first call goes out to the server as a request to get the JavaScript, the browser processes the JavaScript makes another request to the server to transfer the information. If you include two analytics engines, you actually have to make four calls. Temporary redirects are not cached, so the request is always issued. Redirects are always an additional HTTP request
Using GET vs. POST Requests
For GET requests, all parameters are passed in the URL. For POST requests, everything is in the header information. GET requests can be cached easily, because it's assumed that the request doesn't change the server state. POST is never cached, because it changes the state on the server.
For Salesforce B2C Commerce, only GET can be placed in the page cache. POST requests are never cached and are therefore slower than other requests. POST is useful for specific operations, such as login or interacting with the shopping cart. Most requests, however, should use a GET request. For AJAX components, POST requests are also not cached.
Iframes
Salesforce recommends that you generally avoid Iframes if possible. Iframes block the browser onload event and they always have performance cost even if they are empty. This is because each Iframe is a separate HTTP request, which might not be cached. However, Iframes are useful for decoupling the page impression from external services.
Expires and Conditional Headers
Expires and conditional headers are currently not supported in B2C Commerce.