Meta Sr Software Engineer interview questions

Short talk with a recruiter, followed by a phone interview. Phone interview involved talking about my previous projects, why facebook, was there anything that concerned me about the role, etc. It then involved a coding question which i've detailed below:

Recruiter contacted me. First telephonic interview was 45 mins and a single coding question. All interviewers were good except one of the interviewer who asked about system design question (he was rude and wanted to show off). 1) Behavior - prepare for difficult bug etc. questions. What u want to do at Facebook. 2) Lunch 3) System design - give more importance to these type of questions. Asked me about design a system to run a command on all the servers (say 1 million) within the same network from one of the server on the network. 4) Coding - Given a NxN matrix with values X and O where X represent land and O represent water find the number of islands. Two consecutive X X (horizontal or vertical) will be part of single island while diagonal X X are not. (Solve using graph - DFS or BFS) 5) Coding - from list of strings, generate list of list of strings which are anagrams of each other. I did really well, but I guess not good compared to other candidates. Overall interview was easy if you have prepared for Algos and Data Structures. Please give more attention to 1) Writing perfect code on white board. 2) System design questions