YOE: 10 years
Position: equivalent to Google's L4.5 in a Silicon giant tech company

TLDR:
I only reveal a little about interview questions. I read papers in preparing system design.

Amazon:
Online OA and followed by serveral calls with their HRs. Online interviews were 4 sessions, one hour each, while half of the time focusing on tech questions and the other half on leadership questions. Coding questions are LC medium in my opinion, no tricky or tedious problem at all. The hardest question, to me, was something you got to around with inverleaving time segments. From interviewers' reactions, I knew I did pretty well when I finished. The HR called me within a week. However, the TC number is far below my expectation, so I didn't accept it.

Google:
I skipped to onsite directly. 5 rounds of 45 mins each - 4 coding and 1 behavioral.

I was too nervous and got stuck in a trivial equation in my first round, but after taking a deep breath, I managed to finish 4 variations of the problem. In second round, I need to leverage 2 data structures to solve the problem. But once I described my solution, the interviewer asked me to define the interface without actually implementing them and then focus on the core logic. I completed 2 variaions of the problem and then he advanced it to an open question to see how I would approach the as-optimal-as-possible result within time constraint. In 3rd round, the question was a DP problem about LC medium on easy side (well, DP is easy if you find the recursion, but hard if you don't :P), and I solved 2 variations. The last 'coding' session is more like asking you to design a data structure, mostly talking than coding. I didn't give the optinal solution up front, but serveral possible ones, each of which suitable for different senarios, and go from there.

HR arranged my onsite without 'system design round' because I was not so confident in it and nor did I know that it would make it a L4 interview. So after I secured the L4 offer, I asked for an extended interview. You can't find the design question on the internet (yet?), but in the core it's just a classic distributed system question.

I can't reveal the exact questions from my interviews, but I hope you still find my sharing of some use. I didn't feel those popular system deisgn interview materials really helpul to me, though, so I want to share with you how I prepared Google's system design interview.

1. MIT 6.824 Distributed System. I finished most of the classes so as the designated papers.
2. Google's Publication in distrubted system area. I found most of the papers quite a joy to read. I picked old and most-cited papers to read first. As I'm not reading them to become an expert, I skipped related works and benchmark sessions :P Besides the design details, I focus on what kind of problems the system is solving and what trade off had been made.