System Design 365
System design case studies, from first requirement to final architecture.
A structured, open knowledge base for system design interview prep: case studies, high-level and low-level design, patterns, trade-offs, and mock interviews.
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Case Studies
Classic interview systems designed end to end.
High-Level Design
Architecture, scalability, and distributed systems.
Low-Level Design
Object modeling, APIs, and machine coding.
Patterns
Reusable building blocks and techniques.
Trade-offs
Decision frameworks and comparisons.
Mock Interviews
Prompts, session templates, and checklists.
Security
Runtime, supply-chain, and operational risk.
Glossary
Terms you should be able to define cold.
Notes
Free-form study notes.
Latest case studies
URL Shortener
Designing a read-heavy URL shortener at billions-of-URLs scale — Base62 encoding, distributed ID generation, caching, and CDN edge redirects.
Rate Limiter
Designing a distributed rate limiter for a multi-region API gateway — algorithm selection, Redis-backed token buckets, and fail-open semantics.