A case study of a performance tweak causing a bug, including why the bug happened and how to fix it.
Listeners are hard. Do less of that.
Test Driven Development seems like a big win for forcing individual units of functionality to make sense, so let's talk about how TDD encourages moving effects to the outside of the application by making internal mutations difficult to test.
Trying to compensate for a slow API call by optimistically showing success to the user makes for a great experience, but has some pitfalls. Functional programming concepts can help.