0. Introduction: Motivation for Filing Uploads and Downloads So "Slow"

Imagine this scenario: you upload a 10MB high-resolution photo to an image-sharing community, and it takes half a minute to finish. Yet your friend in Beijing downloads it in just 2 seconds. Why does the same file produce such drastically different upload and download experiences?

Or consider this: your e-commerce site runs a Double 11 promotion, and the product detail page suddenly gets flooded with millions of visits—your server goes down completely. Is it insufficient bandwidth? Or a flawed architecture design?

The answers to these questions are hidden in the "golden duo" of object storage and CDN.