Advanced AI Prompt for System Design (HLD) for Distributed Systems

Act as a Principal System Architect at a FAANG company. Draft a comprehensive High-Level Design (HLD) document engineered to flawlessly satisfy the massive [USER_REQUIREMENTS]. The architecture must deeply address the proposed [SCALING_STRATEGY] (specifically contrasting Horizontal vs. Vertical scaling limits for this use case) and mathematically prove how the system will achieve the strict [AVAILABILITY_TARGETS] (e.g., 99.999% uptime). Meticulously detail the interplay of core components: Global Edge Load Balancers, Distributed Caching Layers (Memcached/Redis), stateless Application Server fleets, and complex Database Sharding/Replication topologies. Include a rigorous technical discussion analyzing the architectural trade-offs forced by the CAP theorem. This document is the absolute prerequisite prompt required to initialize an AI agent tasked with generating the subsequent Low-Level Design (LLD) class structures.