I posted on the Compensation board but after many edits I think my post could apply here as well :)
Link

Overview
I was luckily contacted by two sources from both Google and Amazon in October of 2019. I ended up getting offers from both companies.

Experience
Status: 4 years industry experience, BS CS Top 20 CS school
Position: SDE 2 at another top tech company
Location: Seattle, WA

Preperation
Non-LeetCode

• I read the entire Cracking the Coding Interview and looked over the solutions to every problem.

• Memorized and watched all design questions on HackerRank Youtube Channel which is produced by the same author as cracking the coding interview. Specifically, memorize Hashtable, DFS, BFS, Binary Search, MergeSort, BubbleSort, Linked List ... basically everything.

• System design videos all over youtube. Good examples: Whats App or tinyurl

• Example coding interviews on youtube (but most of them were on the easier side and really just as analysis of what kinds of follow up questions to do and how to talk through problems). Checkout interview.io

• Videos from TechLead. Some examples: Mock Google Interview, Let's LeetCode, Why Leetcode Doesn't Work (Although Leetcode does work, just more ideas to discuss) Top 10 Algorithms for Coding Interviews, System Design Interview Concepts

• Less helpful for me but I watched some videos from Clément Mihailescu but directed more towards College Students. Some Examples: Example Google Interview, Coding Interview With College Student

LeetCode
I purchased premium (do it) and looked over/solved all the questions common to both Amazon and Google.
Google Questions Card
Amazon Questions Card
I also did mock interview sessions for Amazon and Google.
For more practice, I just went to the problemset page and sorted by frequency. If I found a problem that I could come up with the answer to in a minute, I skipped it and went to the next problem.
Completed Statistics: 11 Easy, 18 Medium, 7 Hard (like 60+ almost-solved, didn't waste time with small bugs)

Interviews
Done in early Janurary

Google
Onsite (45 minutes each question):

1. Given nodes, tell if they connect Quora
2. Snapshot Array
3. Binary Search Question Something Like this but a little more complex
4. Design a rubiks cube (open ended)
5. Behavioral (How do you prioritize, when did you lead something, etc.)

Amazon
Online Screen (90 minutes for completion):

1. Number of Islands
2. Something like Find all anagrams in a string

Onsite (1 hour per question):

1. Given edges, create a tree and validate (Similar: Graph Valid Tree)
2. Behavioral (But every interview had 30 minutes of behavioral)
3. Design Question: Design subscribe and save
4. Is linked list a palindrome, solve O(n) constant memory (Palindrome Linked List)
5. Design a command line system (looking for use of interfaces, inheritence, extensibility)

Result/Offers

Google
Salary: 150K
Sign-on: 30K
Stocks: 300K
Bonus: 15% Salary (24K)
TC ~280K

Amazon
Salary: 150K
Sign-on: 120K first year, 80K second year
Stock: 180K (5%->15%->40%->40%)
TC ~280K

Was very happy with the process and ended up picking Google after negotating a higher salary to beat the Amazon offer and for benefits reasons (401K match is greater, free food, etc). I also had other co-workers around the team I would be working on.

Hopefully some of this insight helps and helps others negotiate and land a job at one of these tech companies :)