I've been with amazon for 8 years (still an employee) as a software engineer. I've concluded that your experience at amazon - both work life balance and technical - is entirely dependent on your skip manager and your org.
I started with Amazon in the bay area. When I joined we were still in the very early days of our project. The work was awesome, and it felt like we were creating great things. Unfortunately, the ops burden (oncall) became way too much for our team to handle and the quality of life plummeted. My existence during those days was pure pain. From there I relocated (through Amazon) to Seattle to work on something else. I did the move with the promise that I'd immediately get to work on a cool project, but I ended up sitting around doing nothing for months. I didn't even have a desk. Once the project finally started though, things become great. Both of these teams had different VPs, and the cultures of each org were very different as well. My experience in the bay area started off very positively, and then become extremely shitty. My experience in Seattle started off extremely shitty, but then it turned into the most fun 2 years of coding I've done.
Additionally, different orgs do things differently. AWS does things different from how Alexa/Retail/Music/Movies/etc do things. A good example of this: Twitch isn't fully integrated with all of Amazon's internal systems (see recent news for reference). Some teams don't have oncall rotations, other teams have brutal ones. One of my previous directors used to do bi-weekly (once every two weeks) fireside chats. I haven't even met my current director, and I've been under him for a year and a half.
If you're entering the company from the outside, you might very well be walking into a dumpster fire of a team. If you're inside the company, it's really easy to spot which teams are garbage and which ones are not. Below is my guide:
Red Flags: - No nearby principals (no tech guidance at the director level) - Too many principals (bureaucratic arm chair engineering hell) - Average tenure of engineers on the team is SDE1 (trash code) - No PRFAQ/BRDs (projects have no north star, scope is all over the place, dumpster fire product team) - Ops burden is too high (you can check a teams ticket queue on SIM, high ticket count = bad oncall) .... and many more ....
Doing team switches are pretty straight forward as well (ymmv). Once you're in the door at amazon, do your research and determine whether you need to switch teams ASAP. You can search any engineer's username and look at what code they're contributing. It's pretty easy to investigate the code base you'll be working on in advance of joining the team to determine its health.
Regarding tooling, amazon does and doesn't have great tooling. There are things like Pipelines, CR/Crux, Sim/TT, Apollo, iGraph, etc that are actually world class tools and don't really have any rivals out there (yet!). Then there are other things like people wanting to fork bootstrap and react so that they can rebrand it as an amazon version.... In one of my early teams, I saw the SDETs (test engineers) metaphorically go to war with each other to write the best end-to-end integration test framework. There were four frameworks in the end.
Regarding the leadership principles. Those are predominately tools to be used during the decision making process. There is this concept called "one way door decisions" which would be any decision that is made such that the amount of effort needed to undo that decision is not feasible. Basically if you take that door, you can't come back out. When faced with a one way door decision, you use the leadership principles to decide.
Are you on a fixed timeline because your deliverable is tied to AWS Re:Invent? Then you need to optimize for Bias for Action and Deliver Results. Are you about to create a core platform service that many many teams will build on? Obviously you need to optimize for Insist on the Highest Standards, if not you screw over your org for years.
The leadership principles contradict each other, but that generally gives you an idea of what's being gained and lost in the decision making process.
For software engineers, I would not exclude amazon as an employer just because you read some stuff online. If you can get in, do it and stick around for a year or two at least. The amount that you learn in such a short amount of time is significant, and you can take that experience with you anywhere. If you're having a bad experience at Amazon, remember that the company is massive. You can switch orgs and it'll feel like you just changed companies (only the tooling is the same).
Final thoughts: don't ignore your mental health! I have never had a manager actually ask about my mental well being before. I don't think that culture is actually fostered at all at Amazon. Use your vacation time if you have it, switch teams if you need too, or just straight up quit.