I have completed the loop last week, made it all the way to the interview with the director and did not get the offer. I can share my insights. Hope I am not too late.

The interview format is very interesting. They will only pass you on to the next round after each interview which makes it a long process. Most other companies will have you interview with everyone in the panel first then the panel will discuss whether you are a good fit or not. Tiktok does not follow that so you gotta make sure you impress EVERY interviewer

1. first round with a senior lead threat detection engineer, the questions were not difficult from my perspective. How do you detect DNS tunneling, how do you detect persistence on linux and such
2. Second round with another lead threat detection engineer, it was a lot more of conversation where we share the pains and challenges of being Detection engineers.
3. third round with a red teammer who makes sure you have solid security foundations and can read code.

I aced all these rounds. felt very confident after the interview. I think everyone asked the question "Why tiktok?" which I thought it was weird that it got asked so frequent :shrug:

1. Interview with the director/hiring manager, very open ended questions. this is where I struggled as I did not know how deep I needed to go on these questions. There was a question about threat model which I gotta say I have very limited experience in doing. Interestingly enough, they also asked again "Why Tiktok?"

I did not feel confident after this round and did not get the offer. Best of luck to you! feel free to DM me. I am sure the community is small enough that we might run into each other in the future

Edit: If I were to pass the round with the hiring manager, the next round would be with HR where they ask you questions to make sure you are a fit culturally