System Design: See Systems Move: Fully animated, narrated lessons: watch requests flow, caches warm up, databases fail over and queues back up, then tune real simulations to hit an SLO

A visual, hands-on system design course for developers and interview candidates: 14 modules, 56 lessons. Every lesson opens with a narrated animation of a real scenario: requests flowing through a load balancer, a cache warming up as its hit rate climbs, a primary database failing and a replica taking over, a queue backing up during a flash sale, shards rebalancing. Then you practise with checked work: back-of-envelope estimates, choose-the-component and spot-the-bottleneck questions, and simulations where you tune servers, cache size, replicas, partitions and rate limits until the system meets its SLO within budget. Learn estimation, networking, load balancing, caching, databases and storage engines, replication and sharding, consistency and consensus, queues and streams, API design and rate limiting, reliability and observability, storage and search, then design a URL shortener, a news feed, chat, notifications, ride-hailing dispatch, payments, video streaming and autocomplete, and finish with an interview framework and full mock interviews.

14 modules · 56 lessons · 664 practice questions · Intermediate · first module free, then $5

What you'll learn

• Estimate traffic, storage, bandwidth and server counts in minutes, and sanity-check any design with numbers.
• Trace a request from DNS to database and know where the time goes.
• Scale a service with load balancers, stateless servers, health checks and autoscaling.
• Use caches well: pick a strategy, size it, set lifetimes and avoid stampedes and stale data.
• Choose a database for an access pattern, and explain indexes, B-trees, LSM trees and transactions.
• Replicate and shard data, handle failover and lag, and rebalance with consistent hashing.
• Reason about consistency with CAP, PACELC, quorums and leader election.
• Decouple services with queues and streams, deliver messages safely, and survive traffic spikes.
• Design clean APIs with pagination, idempotency keys and versioning, and protect them with rate limits.
• Set SLOs, buy the right number of nines, and stop failures spreading with timeouts, retries and circuit breakers.
• Design real products end to end, and run a system design interview with a clear framework.

Syllabus

1. Foundations and Estimation — What system design is, the numbers every engineer should know, and back-of-envelope estimates for traffic, storage, bandwidth and servers.
2. Networking and the Request Path — What happens between a tap and a response: DNS, TCP, TLS, HTTP, CDNs, proxies, gateways and long-lived connections.
3. Load Balancing and Scaling — Scale up or out, stateless servers, balancing rules, health checks, failover and autoscaling.
4. Caching — Cache-aside and hit rates, eviction and lifetimes, write strategies and invalidation, stampedes and hot keys.
5. Databases and Storage Engines — SQL and NoSQL, data models and access patterns, indexes, B-trees and LSM trees, and transactions.
6. Replication and Sharding — Read replicas, failover and lag, partitioning, consistent hashing and rebalancing.
7. Consistency and Consensus — CAP and PACELC, consistency models, quorums, leader election and Raft, clocks and ordering.
8. Queues, Streams and Async Work — Message queues, delivery guarantees, idempotent consumers, logs and partitions, backpressure in a flash sale.
9. API Design and Rate Limiting — REST and RPC, pagination, idempotency keys and versioning, rate-limit algorithms and a distributed limiter.
10. Reliability and Observability — SLIs, SLOs and error budgets, redundancy maths, timeouts, retries and circuit breakers, metrics, logs and traces.
11. Storage, Search and Data Pipelines — Object storage and blobs, search indexes, unique IDs, batch and stream processing.
12. Case Studies: Core Products — A URL shortener, a news feed, a chat app and a notification system, designed end to end.
13. Case Studies: Real-Time and Money — Ride-hailing dispatch, payments with idempotency, video streaming and search autocomplete.
14. The Interview: Framework and Mocks — A repeatable interview framework and full mock walkthroughs: ticket booking, a key-value store and file sync.