Blog content was stored in memory and it was served with zero-copy to the socket, so yea, it's way faster. It was before times of php-fpm and opcache that we're using now. Back then things were deployed and communicated using tcp sockets (tcp to rails, django or php) or reading from a disk, when the best HDDs were 5600rpm, but rare to find on shared hosting.

The answer is no. The more file is used the longer it sits in kernel filesystem cache. Getting file from cache versus having it in process memory is few function calls away all of which takes few microseconds. Which is negligible in comparison to network latency and other small issues that might be present in the code.

On few of our services we decided to store client configuration in JSON files on purpose instead of running with some sort of database storage. Accessing config is insanely fast and kernel makes sure that file is cached so when reading the file you always get fast and latest version. That service is currently handling around 100k requests a day, but we've had peaks in past that went up to almost a million requests a day.

Besides when it comes to human interaction and web sites you only need to get first contentful paint within one second. Anything above 1.5s will feel sluggish, but below 1s, it feels instant. That gives you on average around 800ms to send data back. Plenty of time unless you have a dependency nightmare and parse everything all the time.