DSA · HLD

High-level design

Distributed system designs — URL shortener, Twitter, Uber — with capacity numbers, components and where they break.

10m
Design a URL Shortener
Bit.ly-class system: Base62 IDs, key-value store, edge cache, ~10× read/write skew.
hldsystem-design
11m
Design Twitter (Timeline)
Fan-out on write vs. read, with a hybrid for celebrity accounts. The classic timeline trade-off.
hldsystem-design
9m
Design Instagram (Photo feed)
Object storage for media, CDN-fronted feed, hybrid fan-out timeline.
hldsystem-design
8m
Design a Rate Limiter
Token bucket vs. sliding window log vs. sliding window counter — and where to deploy them.
hldsystem-design
9m
Design a Distributed Cache
Consistent hashing, replication for read-heavy workloads, and the cache-stampede problem.
hldsystem-design
10m
Design a Chat System (WhatsApp-class)
Persistent connections, fanout per device, store-and-forward for offline users.
hldsystem-design
10m
Design YouTube / Netflix
Adaptive bitrate streaming, edge CDNs, and the upload → transcode → publish pipeline.
hldsystem-design
11m
Design Uber (Dispatch & Trip)
Geospatial driver index, dispatch matching, and the trip state machine across services.
hldsystem-design