Image Hosting
Host images at internet scale — the edge does the heavy lifting.
Serve a front-page image stampede from the edge while an API box dies and the object store slows down.
An image host lives and dies at the edge: a handful of hot images take almost all the traffic, and every byte you can serve from the CDN is a byte the origin never sees. The object store is durable but slow — if misses reach it in bulk, latency explodes long before it falls over.
Components in play
- Image CDN — Serves hot images from the edge — the real product.
- Image API — Resolves image ids, permissions, and variants.
- Metadata cache — Keeps image metadata in memory so lookups skip the store.
- Object store — Durable home of the original image bytes.
Graded on these SLOs
- ≥ 99.00%Images load
- ≤ 100 msImage p99
- ≥ 6.0k rpsSustain the views
- ≤ 85%Origin headroom
- ≤ 6Lean footprint
The brief
Design an image host like Imgur. Users upload images and share links; a tiny set of hot images takes almost all the traffic. Image bytes are big and immutable, so the game is serving them from the edge — the origin and object store should only ever see the long tail.
Functional
- Upload an image and get a shareable link
- Serve the image bytes at that link
- Serve resized variants (thumbnail, feed, full)
Non-functional
- Extremely read-heavy with a hot-set skew — a few images dominate
- Low-latency delivery worldwide
- Durable storage — an uploaded image is never lost
Warm-up: design decisions
Optional theory to prime the calls a senior engineer would make before you build.
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