I work as an IT Engineer at Amazon, and I see some people are saying they are receiving reference letters from CEOs and other high-level people. In a company the size of Amazon, it wouldn’t be reasonable to receive that sort of support from a high-level person.
Would a reference letter from 3 of my managers be sufficient?
There is no strict rule that you need from a C level position. But you should definitely go as high as possible. Org chart can be provided as a small part of your 1 evidence if you need to explain why the referer is a good fit. Otherwisr the referer may explain that in his/her letter, with his strong background in digital tech.
At least reference letters from three different companies would be suggested.
I have heard reference letters from direct managers may not be sufficient because they are not senior enough. At least skip level is recommended.