Toolbox
Interview Trigger: Image / Video / PDF / Backup / Large File
Characteristics:
Cheap / Durable / Massive Scale / Metadata / CDN Friendly
High-frequency Questions:
Why not MySQL? / Why Pre-signed URL? / Why CDN?
Coinbase Scenarios: Avatar / Passport / Receipt / Statement PDF特点
Extremely Durable: AWS S3 有 11 个 9 (99.999999999%)。
Cheap: 比 Redis/MySQL 便宜很多，适合 TB/PB 级别。
Massive Scale: 几乎无限。
Metadata: 每个 Object 可以存 Metadata，例如 Content-Type: image/jpeg。
Interview Follow-up
Q1: Why not store images in MySQL?
Large binary objects increase database size, slow down backups and replication, and make the database inefficient. I’d store only the object metadata or URL in MySQL.
Q2: How do clients upload files?
I’d generate a pre-signed URL so the client uploads directly to object storage instead of routing large files through the application server.
Q3: Why use CDN?
热门头像下载 100 万次，不用每次访问 S3：
Client → CDN → S3减少 Latency & 降低 Cost。