Systems · Week 2
Week 2: Coordination and realtime
Locks, leases, store shapes, messaging hubs, and WebSocket scale.
Week 2: Coordination and realtime
Locks, leases, store shapes, messaging hubs, and WebSocket scale.
Outcomes
- Explain the failure drill for each lesson in this week without notes.
- Complete linked labs where present and keep a short metric log.
- Tag each system with the pattern cards you actually used.
- Distributed leases Time-bounded exclusive rights with fencing so zombies cannot commit.
- Pessimistic vs optimistic locks When to serialize with locks versus version checks — and the failure modes of each.
- Store shapes Picking KV, document, relational, and log stores by access pattern — not fashion.
- Realtime messaging In-process fan-out hubs before you reach for a broker.
- Scaling WebSockets Connection fan-out, sticky routing, and horizontal limits.