Module 01
Core building blocks
- Load balancing (L4 vs L7)
Send requests through an L4 or L7 balancer and watch L7 route by path to specialized pools while L4 only sees IP and port.
- Weighted round-robin & health checks
Kill a backend mid-request and see how health-check interval and retry policy decide how many requests fail before traffic drains away from it.
- Consistent hashing & virtual nodes
Add or remove nodes on a draggable ring and count, with highlights, exactly which keys move, first without virtual nodes and then with them.
- Service discovery
Autoscale instances in and out and compare client-side and server-side discovery, including the window where a newly registered but unhealthy instance receives traffic.
- API gateway & request aggregation
Watch a gateway authenticate a request, fan it out to several services in parallel, and decide what to return when one of them times out.
- Back-of-envelope estimation
Adjust DAU, read:write ratio, and record size with sliders and watch QPS, storage growth, and bandwidth recompute, with each step of the arithmetic shown.