This article is about some of the basic and important steps to be used to improve the performance in web-sphere commerce application development.
1) Always leverage the Dyna-caching facility provided by the product
2) Remove the unwanted code from JSP when you are customizing the store for your need.
3) Look for <wcf:getData tags and see if you are still using them
4) Reduce the usage of data beans in nested forEach loops
5) Make sure that background Ajax calls will not take more than 2 seconds. So that that you avoid the bad state of attribute and cookie values
6) Mostly web sphere commerce out of the box code will have all the feature supported and the code will be checking for all those feature. If your business requirements are not needed all those features try to remove the unused code, attributes and checks.
8)Whenever possible try to do minimal change on the out of the box(OOTB) features to achieve your customized features.
9) Dojo widgets are used by customizing in WC. When you need some more web 2.0 features you can use the Dojo toolkit itself or you can use jQuery.
10) Try to get the preliminary validations at front end. Like quantity, names, login etc. And some of the specific secure business flows in backed as well.
11) Use common variable include in the JEnvironmentSetup.jspf
12) Use JSP comments for comments like <%-- Some comments --%> and avoid big comments in html comments <!-- Some Html Comments -->
13) As much as possible reduce the white spaces being rendered in JSP.
14) Move all customized JS code to a .js file and include
15) Minify your toolkit js included.
16) Make sure that valid types and media types are used for resources.
17) Look for all the images are existing in the system. And page will not spend time looking for resources and handling the exception scenarios.
These are some basic tips I found while developing multiple customized stores in web sphere commerce product.