Slide 54 is insanely important. At my current place we've invested tons in instrumentation and metrics. Every IO operation is guarded with a semaphore and access is monitored and exposed. Every cache in the system logs everything from hit and miss rate to volume etc. Every async operation logs operation trails. We also ship a ton of tools for everything from bread and butter stuff like stack dumping, pinpointing long running threads etc. to more sophisticated stuff like being able to break in to a page rendering and profiling various element hierarchies, either over time or following specific users.

As I said, we've invested so much in getting the entire stack monitored very granularly, but every time our customers run in to issues it pays dividends.

For reference, we run on the JVM which is very pleasant. A ton of tools interop with it and basic things like MBeans being integrated in to JVM makes monitoring a lot easier.