Distribution of execution between phases of I/O callbacks in node.js

Question

The node.js event loop is still so poorly described in the documentation that we have to ask more questions..

There are two phases: pending callbacks and poll, both, as the documentation says, executes I/O callbacks. But the difference is that the pending callbacks phase will executes deferred I/O callbacks.

How do I know when deferred I/O callbacks are executed?

Answer that I expect: Practical code examples that could clearly indicate in which phase I/O callbacks will be executed.

_{P.S Another one question to which there will most likely not be an answer.}