A course in system design

Most people read about system design.
Far fewer have felt it move.

58 lessons, ordered from first principles to five full case studies — with a working simulator dropped into the ones where intuition is hard to come by.

Begin the course Browse all 58

58: lessons; 3h 38m
10: simulators; inside the lessons
52: flashcards; 31 lessons with quizzes
180: articles; linked, never copied

Specimen

Lifted straight out of the Consistent Hashing lesson. It works here too — add a node.

Consistent hashing ringAdd or remove a node and watch how few keys actually move.

Nodes

Keys remapped

—

With naive hash(key) % N, changing N remaps almost every key. On the ring only the keys in the affected arc move — roughly 1/N of them.

user:1	A
user:2	B
cart:9	B
sess:a	B
img:42	B
post:7	C
ord:3	B
tag:z	B

Built so you actually reach the end

Simulators, not screenshots

Ten lessons carry a working model of the thing they describe. Add a node to a hash ring and watch which keys move. Burst a token bucket until it throttles. Shard one table three ways and read the skew.

Open the hashing ring