System Design Building Blocks

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reading · we frame, you read MIT or the canonical taught · we author, no canonical fits ↺ spirals back to earlier lessons

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reading · 30 min + ~190 min canonical

Load Balancers and Caching Strategies

The last course gave you the method for designing systems; this one is the catalog of parts you design with — the standard building blocks, each studied deeply enough to use well.…

primary System Design Interview Vol 1 by Alex Xu — Building block chapters

preview →

reading · 30 min + ~190 min canonical L1

Message Queues and Event-Driven Architecture

A message queue is the building block that lets parts of a system talk asynchronously — one component drops a message and moves on, another picks it up and processes it later, and…

primary System Design Interview Vol 1 by Alex Xu — Building block chapters

after L1 locked

reading · 30 min + ~190 min canonical L1

CDNs, Blob Storage, and Content Delivery

Two building blocks solve two problems that a database is spectacularly bad at: serving content fast to users far away, and storing large files. The CDN (Content Delivery Network)…

primary System Design Interview Vol 1 by Alex Xu — Building block chapters

after L2 locked

reading · 35 min + ~190 min canonical L1

Search and Ranking: Inverted Indexes, Relevance, and PageRank

"Find all documents containing these words, and show me the best ones first" is one of the most common and deceptively deep features in software — and it's a specialized building …

primary System Design Interview Vol 1 by Alex Xu — Building block chapters

after L3 locked

reading · 35 min + ~190 min canonical L1

Rate Limiting, Consistent Hashing, and the Infrastructure Glue

This lesson closes the building-block catalog with three kinds of component that hold distributed systems together: rate limiting (protecting a system from being overwhelmed — by …

primary System Design Interview Vol 1 by Alex Xu — Building block chapters

after L4 locked

exercise reading · 15 min L1

Exercises: Easy (Warm-up)

- [ ] Implement a token bucket rate limiter in Ruby — allow? method with refill logic - [ ] Implement cache-aside pattern in Ruby with Redis — get checks cache, misses go to DB, s…

after L5 locked

exercise reading · 30 min L1

Exercises: Medium (Core)

- [ ] Implement consistent hashing in Ruby — Hash ring with virtual nodes, add/remove server with minimal redistribution - [ ] Build a simple message queue in Ruby — In-memory que…

after L6 locked

exercise reading · 45 min L1

Exercises: Hard (Stretch)

- [ ] Design a Web Crawler — AX Ch9 — Politeness (robots.txt), URL frontier, dedup (Bloom filter), distributed crawling - [ ] Design a News Feed / Timeline — AX Ch11 — Fan-out on …

after L7 locked

exercise reading · 60 min L1

Mini-Project

- [ ] Build a URL shortener in Ruby (Rails) — End to end: Base62 encoding, Redis cache, click analytics with counter, rate limiting, custom aliases; deploy and load test with wrk

after L8 locked

L10

project reading · 300 min L1

Project: Rate Limiter Comparison

Implement 4 rate limiting algorithms in Ruby: token bucket, leaky bucket, fixed window, and sliding window log. Benchmark each under bursty and steady traffic patterns. Write up t…

after L9 locked

L11

project reading · 300 min L1

Project: Cache with Eviction Policies

Implement an in-memory cache in Ruby supporting LRU, LFU, and TTL eviction. Each policy is a strategy (Strategy pattern). Benchmark hit rates under different access patterns (unif…

after L10 locked

L12

assessment reading · 63 min L1

Self-Assessment: System Design Building Blocks

- [ ] Explain four caching strategies: cache-aside, write-through, write-behind, and refresh-ahead. - [ ] What is consistent hashing? How do virtual nodes help with load distribut…

after L11 locked

12 lessons. Read in order; spiral back when you need to. By the end you'll have used the core ideas twice — once on the abstract, once on something you'll meet at work next week.