I interviewed for google L4 Position almost 2 months ago, and gave 3 rounds of DSA, 2 were planned before-hand, in first round I got a lean-hire, and in the second round I got a no-hire, which is why the recruiter scheduled a third round and told me that I need a above hire rating for my package to have a good case in front of the hiring committee.

Now, let me tell you about the difficulties that I faced in the google DSA rounds, at least from my perspective.

1. About the questions : They will give you a medium problem to a medium-hard problem, assume it is the first time you are seeing the problem, and you have 45 minutes to solve 2 such problems.

2. Rating-flaw - Even if you are able to code a decent enough solution, but maybe the interviewer gave you 2 small hints, like for example you just forgot to write a return statement somewhere, or maybe something else, the exacts are not important here, so for every hint they will reduce your rating by 1. So lets say you get Strong-hire if you solved without any help, which can only be the case if you have done the problem earlier (or maybe you are very well prepared), but that wont be the case most of the times.

3. Time-complexity analysis : This is not a flaw, but just an important thing to keep in mind, google interviewer will damn sure ask you for your code's time complexity, which at-least I didnt heed to during my preparation, and if you make a mistake there then thats 1 more degradation in rating. So my advice to anyone going to interview would be to at least practice computing the time complexity for 20-30 questions so that you have a step by step mechanism to go about it.
4. Time-constraint problem : In my interviews the interviewer wont go to the second problem if I am unable to make progress in the first problem, this might be standard across companies, but what I feel is that, sometimes in the heat of the moment, you are just not able to make sense of a problem statement, plus the clock is ticking against you, so if the interviewer just gives you the second problem as well, and suppose you are able to solve it, then you can comeback to the first problem with a positive mindset and might even be able to solve it.

Last, google hiring process is extremely slow, so you have to be patient, and I would recommend you to also interview with other companies in-parallel so that even if you dont end up getting an offer from google, at least you would have something from the other companies, or be in-process of getting.

Wishing good luck in your journey!

Edit 1 : The agenda of this post is to make the future candidates prepare better, and learn from the mistakes that I made; the agenda of this post is not to say that I was the best coder out there and still google didnt hire me, google hiring process sucks.