Here's how a typical Meta coding round goes:
Minutes -: Introductions. Your interviewer describes the problem.
Minutes -: You ask clarifying questions. Input types, edge cases, constraints.
Minutes -: Solve problem . Explain your approach, code it, test it.
Minutes -: Interviewer gives problem (often a follow-up or related problem).
Minutes -: Solve problem .
Minutes -: Your questions for the interviewer.
Two problems per round means you have about minutes per problem. Practice under time pressure.