I've been working at well-known tech companies since 2012, in London and Amsterdam: at Skype/Microsoft (when Microsoft acquired Skype), at Skyscanner (when it became a unicorn) and at Uber for the past three years. I've had many conversations with people online and offline on what it's like to work at places like this, compared to other environments: from what the work culture is, to how things get done, how things are tested or how much truth there is to some of the articles you might read online - and many more.
Feel free to ask anything about work, career, engineering practices or anything else you find interesting or are wondering about.
As a disclosure, I can't talk on behalf of the companies themselves - they're all very large, so whatever my observation was, might not be true for all parts (and it might also be outdated knowledge). I can definitely share my experience, learnings, and patterns I've seen to hold across these kinds of places.