Now he talks about how to decouple APIs from the underlying systems.

This is something where I still see a lot of resistance because many engineers
have limited experience with these designs and are used to interact with 10-20
year old synchronous REST APIs.

The more important and popular a service is in your system is, the more you need
to look I to catching it. Because if the backend for it goes down you don't want
to have your users hitting your failing services over and over.

If you add data to a database that is going to be mutated in the next 20-30
seconds it does NOT belong in a database. Put it in a memcache and persist it
once in a while.