02
Foundation · Case Study 2
URL Shortener
Design bit.ly — takes a long URL, returns a short code, redirects at scale. 100M DAU, 1B redirects/day.
System Requirements
Functional requirements, back-of-envelope estimation, NFRs, API design, and base architecture.
FREstimationNFRAPIBase Architecture
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Deep Dives
Short code generation, database sharding, caching strategy, peak traffic handling, pre-generated keys, cold storage, and fault isolation.
Short Code GenShardingCachingPre-Gen KeysCold Storage
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Observability
SLIs and SLOs for a redirect service, latency P99 measurement, availability tracking, alerting, and error budgets.
SLI / SLOAlertingError Budget
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Final Design
The complete architecture after all deep dives — every component justified, every tradeoff resolved, full system diagram.
Final ArchitectureFull Diagram
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