I myself was very ashamed of a company I worked for (also SF based) blog post... even the author of the post was a very well known open source maintainer of many libraries of a very popular programming language. Reading the posts in the blog was like.... I cannot believe we lie this big... internally things were just crap, and what the blog post made look like it was the norm, was just a side project of this person.
So, never trust companies blog posts by default.
I remember interviewing a candidate once who said he was excited about the role because of that A/B testing blog post, and I just thought - geez what a completely soulless bait and switch ploy.
Facebook, Amazon, Netflix Google, Microsoft comes to the top of my head but someone is free to burst my bubble.
Questions get answered quickly and with a level of detail appropriate to the person asking.
Really impressive given the usual "Enterprise(TM)" level of support from most service suppliers.
EDIT: To be clear, there is no "the DB" at Uber. It was the main database flavor that the larger teams used, but they used everything at Uber, from MySQL to postgres, to mongo, etc. Sometimes with things on top, sometimes directly. For more analytical/financial things, they used HBase/Hadoop/Cassandra, or even older things like old IBM database tech from the 80's. Really weird mix of stuff, and it really depended on which high-profile engineers they hired in which part of the company.
They were trying to hire (and poach) just about anyone they could around this time. Therefore, these articles are... very shiny, compared to the actual tech applied internally (note that even though Uber is referred to in the third person here, this is on uber.com and written by an Uber employee).
I worked at Uber for a year. Schemaless was... meh. Nobody really liked using it, nobody really understood it, and you weren't really allowed to host your own instance - you had to have another internal team do it for you, which didn't help the "understanding" problem.
It smelled distinctly of "not invented here" syndrome. A number of things inside Uber worked that way - the culture was so competitive and brutal, performance reviews were always a massacre, so everyone was trying to outshine their peers (or outright climb on their backs, etc).
This resulted in a LOT of "tech" being "invented" that 1:1 did something already prominent in open-source or was already an enterprise solution (probably cheaper than paying engineers to do it) but since actually achieving it and having your name on it meant you would look better for a promotion or a bonus or whatever over a colleague meant it was worth it to the individual to reinvent the wheel. Rinse and repeat over and over again.
I'm not an enemy of reinventing the wheel, mind you. But only if the new wheel works significantly better than the old one. This was rarely the case at Uber.
Postgres was still used somewhat commonly at Uber when I was there, but they were really pushing for Schemaless internally. It felt very overkill for just about everything outside the platform teams and was always, without fail, a massive pain to deal with.
Don't be fooled by these Uber engineering articles. This was PR to bolster up their OSS image to outsiders to help with hiring and poaching at the time. Things internally looked very different.