Labs
One idea, one system, ten minutes.
No narrative and no sections. Each lab is a running system with a single behaviour worth understanding, and the fastest way through it is to break something.
Cache Simulator
Tune hit ratio and TTL against a fixed database, and find the point where the tail collapses.
beginner~10 min
Load Balancer Simulator
Distribute traffic across replicas, then remove them one at a time and watch the survivors.
beginner~8 min
Queue & Backpressure Simulator
Build a backlog by outrunning your workers, then discover how long it takes to drain.
intermediate~12 min
Replication Lag Simulator
Write to the primary, read from a replica, and watch the two disagree.
intermediate~10 min