System Design L6
Staff-level system-design case studies: define correctness, find bottlenecks, recover safely and limit blast radius.
30 lessons · about 0.5 hours
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The learning loop and a repeatable interview framework.
Core System Design Concepts
Capacity, traffic, APIs, data, caching and communication building blocks.
- 07Capacity, Availability, Latency and CAP The constraints that shape every distributed design: load, response time, uptime and partition-time policy.
- 08Caching, Consistent Hashing and Sharding Move reads close to users, distribute data safely, and understand cache and database consistency costs.
- 10Proxies, APIs and Real-Time Protocols Pick REST, RPC, queues, long polling, WebSockets, TCP or UDP based on the interaction shape.
- 11Batch vs Stream and Data Modeling Choose when work runs and shape data for correctness first, then deliberately denormalize proven read bottlenecks.
- 23Networking, DNS and Traffic Routing Understand the request path from OSI layers and DNS through load balancers, anycast and reverse proxies.
- 24API Contracts, Gateways and Security Make APIs evolvable and safe with explicit formats, versioning, idempotency, gateway policy, authentication and authorization.
- 25Real-Time, Pub/Sub, Webhooks and CDC Choose the right push or event mechanism and keep event delivery observable, idempotent and replayable.
- 26Database Internals, Replication and Scaling Connect storage-engine choices, durability, replicas, query plans, pooling and data layout to real production behaviour.
Distributed Reliability
Correctness, coordination, overload control, time and scale-oriented data structures.
- 02Exactly-Once Payment Processing Safe payment retries need a durable idempotency record, atomic state transition and provider-side deduplication.
- 03Timeouts, Retries & Backpressure A slow dependency should consume a bounded budget, not create an infinite retry storm.
- 06Debug Latency Like an Investigator High CPU is not required for high latency. Follow percentile shape and trace wait time before scaling blindly.
- 09Distributed Coordination: Consensus, Heartbeats and Gossip Use strong agreement, lightweight failure detection, integrity checks and membership propagation for the right problems.
- 27Time, Consistency and Distributed Transactions Reason about clocks, ordering, split brain, locks, CRDTs and transactions without promising impossible global certainty.
- 28Data Structures for Scale Use geospatial indexes and probabilistic structures to make huge queries practical while understanding their error bounds.
Architecture and Operations
Choose system shapes, analytical platforms and safe production releases.
- 19Architecture Patterns at Scale Choose client-server, microservices, serverless, event-driven or peer-to-peer architecture based on ownership, failure boundaries and operational cost.
- 29Big Data: ETL, Warehouses and Streaming Build reliable analytical pipelines with batch/stream processing, lake and warehouse layers, and explicit freshness contracts.
- 30Releases, Observability and Production Safety Ship changes safely with rollout strategy, flags, migration discipline, rollback plans and observable service-level outcomes.
Case Studies
Apply the concepts to real production-style design problems.
- 04Flash Sale: 10 Million Buyers, No Oversell A queue smooths traffic but does not reserve stock. The durable inventory owner decides the winner atomically.
- 05Premiere-Night Video Streaming Let millions press Play together by separating small control-plane APIs from CDN-delivered video bytes.
- 13Design a URL Shortener Generate durable short links, redirect in milliseconds, prevent abuse and keep analytics off the redirect path.
- 14Design a Chat Application Deliver live messages without losing them by separating durable messages from fan-out, presence and offline notifications.
- 15Design a Ride-Sharing Service Match riders and drivers with a geo index, safely lease availability, and treat location as a fast-changing stream.
- 16Design a File Storage Service Upload bytes directly to object storage while the API owns durable metadata, authorization, sharing and synchronization.
- 17Design a Polite Web Crawler Crawl at scale without revisiting endlessly or overwhelming hosts: normalize, deduplicate and schedule per host.
- 18Design a Reliable Notification System Deliver email, SMS, push and in-app messages with preferences, isolation, idempotency, provider failover and auditable states.
- 20Design a Social Media Feed Build a fast home feed with fan-out choices, durable post storage, eventual consistency and safeguards for celebrity hot keys.
- 21Design an E-Commerce Checkout Keep browsing scalable while protecting the correctness-critical path: inventory reservation, idempotent payment, order creation and durable events.
- 22Design a Logging and Monitoring Platform Ingest high-volume telemetry reliably, separate hot search from cheap retention, and make alerting useful rather than noisy.