I interviewed for 4 different roles (2 frontend, 2 backend) and failed all of them. I felt like I wasted my time because I was deemed not to have enough experience for 2 roles only after the final round, which should have been noted earlier during the resume screening.

The interviews are very team-dependent. For backend interviews, expect many CS fundamentals topics in the first 30 minutes for most teams in the first 2 rounds. To prepare, revise everything such as concurrency, networking, caching, and programming languages you state you know on your resume. The last 30 minutes typically involve solving 1-2 LeetCode Medium questions.

For frontend interviews, expect questions related to JavaScript, TypeScript, React, networking, and any other FE libraries or frameworks you mentioned on your resume. Most coding questions for frontend interviews weren't typical DSA questions. Search LeetCode for questions filtered by "javascript"; those are the types of questions you will be asked to code.

The hiring manager round for both backend and frontend focused on resume deep dives and system design.

Tiktok is open to candidates interviewing for another role anytime after failing an interview for a current role. They seem quite desperate to hire due to their infamous high turnover rate. Contacting any recruiter via LinkedIn can get you a referral, potentially allowing you to skip the Online Assessment. I never had to complete a single Online Assessment for any of the 4 teams I interviewed with.