An ideal blog post probably provides answers to others who may be searching. This one doesn’t. This is the accounting of the mysteries of “localhost” on CentOS linux instances. I’ll post updates as I actually start to understand the answers.
Fetching a web page from localhost is slower than fetching from 127.0.0.1
127.0.0.1: average response .015s
localhost: average response .166s
So an entire end-to-end fetch is ten times as slow using localhost, and the IP address is apparently not cached, as it doesn’t get any faster with repeated runs.
Yes, “localhost” is an alias to 127.0.0.1 in my hosts file, so I expect that an actual DNS request on the wire should not be necessary.
WordPress won’t find my database on host “localhost”, but it will find it at 127.0.0.1