TikTok IOS Software Developer interview questions

Had 2 technical interview over zoom, 45 minutes each. Pretty good sessions, but I didn't pass. Both interviewers are Chinese, based in Shanghai, but good English. Started on time, and ended on time too. The 1st round consists of asking fundamental iOS questions, and last 20 min solving a coding problem (easy difficulty). The 2nd round is designing the architecture of a photo browsing app, and in the process will ask about ways to optimize.