Act as a Senior Systems Architect. Design a multi-layered caching strategy for a global e-commerce platform experiencing high read/write contention. Your strategy must address: 1) Cache invalidation protocols (Write-through, Write-back, or Write-around with justification), 2) Handling cache stampedes, 3) Data consistency across different geographical regions (eventual vs. strong consistency trade-offs), and 4) Mitigating the 'thundering herd' problem during flash sales. Provide a detailed architectural diagram description and pseudocode for the cache-aside logic.