Quiz

Daily questionToday's question is on the boardOne attempt · +11 XP
Quick quiz

Five questions from every level, easiest first · +5 XP each

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Quizzes by phase

00 · Scale From Zero

Lesson: What is System Design?Lesson: ScalabilityLesson: Life of a Web Request00.1 · The scaling journey, step by step00.2 · Stateless web tier & auto-scaling00.3 · Multiple data centers & geo-routing

01 · Mental Models

Lesson: Latency, Throughput & Availability01.1 · Why systems fail at scale01.2 · Latency numbers every engineer must know01.3 · Back-of-envelope estimation01.4 · CAP theorem — the fundamental constraint01.5 · Consistency models spectrum

02 · Data Layer

Lesson: SQL vs NoSQLLesson: Indexing & ReplicationLesson: Sharding & CAP Theorem02.1 · SQL vs NoSQL — the real decision framework02.2 · Indexing — why queries are fast or slow02.3 · Database replication02.4 · Database sharding (horizontal partitioning)02.5 · Consistent hashing

03 · Core Components

Lesson: Load BalancersLesson: CDNs & ProxiesLesson: Caching StrategiesLesson: Message Queues & Pub/Sub03.1 · Load balancers03.2 · Caching — the highest leverage optimization03.3 · Message queues & async processing03.4 · CDN & blob storage03.5 · Rate limiting03.6 · Search — full-text & beyond

04 · Patterns & Principles

Lesson: API Design & Rate Limiting04.1 · Proxy patterns — forward & reverse04.2 · Event-driven architecture & event sourcing04.3 · Fault tolerance — building for failure04.4 · Distributed transactions & the saga pattern04.5 · Unique ID generation at scale04.6 · API design — REST, GraphQL, gRPC

05 · Observability

05.1 · Metrics, logging & distributed tracing

06 · Security

06.1 · Authentication & authorisation

07 · Practice Questions

Lesson: Design a URL Shortener07.1 · Design a URL shortener (TinyURL)07.2 · Design a chat system (WhatsApp)07.3 · Design a news feed (Twitter/Instagram)07.4 · Design a video streaming platform (YouTube)07.5 · Design a ride-sharing system (Uber)07.6 · Design a key-value store (Redis)07.7 · Design a rate limiter service07.8 · Design a notification system07.9 · Design search autocomplete07.10 · Design a distributed cache07.11 · Design file storage and sync (Dropbox)07.12 · Design a web crawler07.13 · Design a ticket booking system07.14 · Design collaborative document editing07.15 · Design a distributed job scheduler

08 · Distributed Systems

08.1 · Quorums & tunable consistency08.2 · Leader election08.3 · Consensus: Raft and Paxos08.4 · Vector clocks & conflict resolution08.5 · Bloom filters08.6 · Merkle trees08.7 · Distributed locks08.8 · Gossip protocol

09 · Infrastructure & Delivery

Lesson: Monolith vs Microservices09.1 · Service discovery09.2 · Monolith vs microservices09.3 · Deployment strategies09.4 · Chaos engineering09.5 · Real-time delivery: polling, SSE, WebSockets09.6 · The secure request path: DNS, TCP, TLS, HTTP09.7 · Incident response and on-call09.8 · Blameless postmortems

10 · Data: Beyond the Basics

10.1 · ACID vs BASE10.2 · Row vs column stores and data warehouses10.3 · Time-series and graph databases

11 · Senior Engineering

11.1 · Storage engines: B-trees vs LSM trees11.2 · Stream and batch processing11.3 · SLOs, error budgets and cost11.4 · Multi-tenancy and isolation11.5 · Threat modelling and data privacy11.6 · Data modelling and online migrations11.7 · Design a payment ledger