The interview process consisted of two rounds of phone interviews, featuring three algorithm questions ranging from easy to medium difficulty on LeetCode, and one coding question with iOS-specific elements.

The onsite interviews included four sessions:

• The first session was a behavioral interview paired with a coding question.
• The second was a design session, which was very intense with many details being asked.
• The third interviewer asked questions about concurrent programming before moving to a coding question.
• The fourth interviewer presented two coding questions; the first was easy, and the second tested overall iOS knowledge.

My suggestions are: ensure you have practiced all easy and medium LeetCode questions relevant to the Facebook interview process before your interviews. Otherwise, you likely won't have a chance. Beyond coding proficiency, you need to be bug-free and demonstrate optimized algorithms. The design question is experience-oriented, so make sure you thoroughly understand most app components, especially service/network-related parts.

Overall, the experience was great. I met some talented iOS developers, and discussing their work experiences, I observed that everyone seemed very happy with their lives there. I hope to update this with a positive result sometime in the future. I haven't heard back from them yet.

The questions are not particularly difficult, but ensure your code is bug-free, clean, and quick.