Keep in mind that the author of that blog doesn't actually talk to anyone at the company they are writing about, they just collect articles around the internet and public statements and piece it together from that.
For example one of the most popular article on that site (which is part of their book now) is the article on Netflix. A lot of that was cribbed directly from my talks, but they never reached out to me to even check it over, and as such missed a lot of nuance and detail, things I didn't cover in my talks.
Same thing for the article about reddit -- also cribbed a lot from my talks.
It's a fine overview, but light on specifics. I've reached out a few times and some things have been corrected after the fact, but I don't know if the other articles have been reviewed.
So my point is, be warned that the articles on that site are not primary sources but are derived from them.
Other times, they would directly talk to a single employee, but get skewed or misleading information based entirely just on that one employee's POV.
Their post about Tumblr's architecture [1] focused a lot about JVM-based services, HBase, etc which in reality was only ever used for a tiny subset of the backend. The huge section on "Cell Design for Dashboard Inbox" was especially ridiculous: the systems described there were literally a mix of complete vaporware and failed/canceled projects that never even got close to production.
As an early Tumblr engineer, I was really upset to read this nonsense. I spent several months of my life working very long hours to successfully scale the existing (PHP/MySQL) dashboard activity feed architecture in 2011-2012. It continued to be used as-is for many years after this interview, with lower latency and much lower cost than the proposed hbase/scala cell replacement.
And of course, engineering candidates being interviewed would always ask about this hbase cell architecture thing that they read about in High Scalability...
http://highscalability.com/all-time-favorites/