Welcome to the architectural design review board. Our startup has just secured $100M in funding, and we project a 100x user growth in the next year. As the new CTO, your task is to present and justify your proposed system architecture. Assume you are addressing a critical technical board. For each section, clearly state your proposed solution(s), provide detailed justifications based on the given scenario (100x growth, social media), discuss the pros and cons/trade-offs of your choices, and address potential alternative approaches and why you opted against them. Emphasize how your design ensures scalability, reliability, performance, cost-effectiveness, and maintainability. The depth of your answers and your ability to foresee and mitigate challenges will be key.

For the Database Sharding Strategy section (Weight: 25%):\n\n1. Identify and justify the primary sharding key(s) for a social media application (e.g., user ID, content ID, time-based, geographic). Discuss the implications of each choice on data locality, query patterns, and cross-shard operations.\n2. Propose strategies to handle hot spots and facilitate seamless data rebalancing as the user base grows by 100x. Include considerations for data migration.\n3. Discuss the choice of consistency models (e.g., strong consistency, eventual consistency) for different features within a sharded environment and their trade-offs in a social media context (e.g., user feeds, friend lists, message delivery).

For the CQRS (Command Query Responsibility Segregation) Implementation section (Weight: 20%):\n\n1. Justify the adoption of CQRS for a high-throughput social media platform, specifically for core features like user posts, likes, comments, and real-time feeds. Explain where CQRS provides significant advantages over a traditional CRUD model.\n2. Describe the typical components of a CQRS architecture in this context (e.g., command service, event store, read models/projections, query service, message brokers) and how they interact.\n3. Discuss how eventual consistency inherent in CQRS might impact user experience for specific features and propose mitigation strategies to enhance perceived consistency.

For the Message Queues for Asynchronous Operations section (Weight: 20%):\n\n1. Identify at least three critical areas in a social media platform where message queues are crucial for scalability, decoupling, and resilience (e.g., notification delivery, asynchronous feed generation, analytics processing, image/video transcoding, fan-out mechanisms).\n2. Describe the benefits of using message queues in these contexts (e.g., resilience against service failures, load leveling, decoupling services, efficient fan-out) and potential challenges (e.g., message ordering, dead-letter queues, ensuring 'at-least-once' or 'exactly-once' processing).\n3. Propose a suitable message queue technology (e.g., Kafka, RabbitMQ, SQS/SNS) and justify its selection based on the expected scale and specific use cases.

For the Global Content Delivery Networks (CDNs) section (Weight: 15%):\n\n1. Explain the comprehensive role of a CDN in delivering various types of content (e.g., user profile pictures, videos, trending feeds, static assets, dynamic API responses) globally to minimize latency and offload origin servers.\n2. Discuss advanced strategies for optimizing CDN usage, including cache invalidation mechanisms, edge computing logic (e.g., Lambda@Edge), and origin shielding.\n3. Address challenges related to global data consistency across CDN edges and compliance with local data residency regulations (e.g., GDPR, CCPA) for a global social media platform.

For the Holistic System Resilience and Future-Proofing section (Weight: 20%):\n\n1. Discuss comprehensive strategies for proactive monitoring, robust alerting, and efficient incident response for a distributed system at this extreme scale.\n2. Outline a detailed plan for disaster recovery (DR) and business continuity, considering multi-region deployments and recovery time objectives (RTO) / recovery point objectives (RPO).\n3. Address how the chosen architectural patterns facilitate future feature expansion, rapid iteration, and adaptation to new technologies without requiring major re-architecting.\n4. Consider critical security implications across the entire distributed system, including authentication, authorization, data encryption (at rest and in transit), and protection against common web vulnerabilities.