Time for the performance questions in my 2015 survey. A favourite topic of mine, and my boss, Penny Cookson, lives for tuning.
Q9. How do you proactively address performance? (tick all that apply)
Tune SQL - I would be surprised if this wasn't the top result. Plenty of SQL used in APEX applications, and why not tune them?
Limit Interpreted PL/SQL - this is good practice in general, but in the world of APEX, this means moving inline code from application into packages. You can get pretty quick wins doing this with any plugins. Read here for details.
Materialised Views - a database construct that can aggregate complex information at regular intervals, to be queried many times with simpler SQL over fewer rows. I've seen interesting examples that obfuscate layers to external information using pipelined functions. Or you could just use it for your menu.
Care using v() - Particularly important when referencing page items, since this function would execute a query on the session state table. While values such as APP_ID come from a persistent package variable, it's still context switching between SQL and PL/SQL, so it would be even better to use bind variable.
where id = (select v('APP_ID') from dual)
I think any use of v() should be questioned. SQL queries should use bind variables (not substitution strings) and packages should be parameterised.
Page Workflow/Design - why refresh the entire page when a partial refresh would do? A well designed application will limit network traffic and the amount of queries necessary to serve the data. Refreshing regions on demand with dynamic actions is one of the most regular things I do. Declarative page modals in APEX 5.x have also made APEX life a lot more comfortable.
Global Page Modularisation - Performance also about the developer not repeating tasks over and over, causing future maintenance headaches.
JSS/CSS File Management - minifying code can reduce network traffic, as can well designed libraries; CDNs; and declarative options. I understand APEX Front End Boost can help.
Care with jQuery selectors - selectors can be abused just like table indexes. I have some commentary on this here.
Region Caching - possibly underutilised, but the ability to cache region on the global page in APEX 5.0 opens options, as do some new APIs.
data-attributes - jQuery related, what I meant by this was to offer more information during report generation, which can help interactivity and reduce AJAX activity. Though read consistency issues should be considered. See a basic example here.
Other - a few people suggested a well designed data model. Touche. Even more got stuck into it in the next question on performance return on investment.
The User Interface attributes are also an area worth being familiar with, particularly in regard to application level file management.
I don't need to worry about performance - yeah, right.