Design an Online Minesweeper Platform

Design an online Minesweeper platform for web and mobile users. Requirements: - A signed-in user can start a new game with standard or custom board sizes and mine counts. - The first click must never hit a mine. - Users can reveal cells, place or remove flags, pause, resume, and finish a game. - Revealing an empty cell should automatically expand the connected zero-neighbor region. - The system should persist in-progress games. - The platform should maintain global and friends leaderboards for completed games. - Ranked games should be validated by the backend to reduce cheating. - Assume about 1 million monthly users, 50,000 daily active users, and up to 5,000 concurrent games. Target low-latency moves with roughly sub-100 ms perceived response time. Discuss the functional requirements, APIs, data model, game-state management, storage, scaling approach, and anti-cheat trade-offs.