Load Balancing & Scaling
One server becomes twenty behind a single address, and nobody on the outside can tell.
5 lessons · ~50 min · free
By the end you can
- Argue vertical vs horizontal scaling with the real trade-offs
- Pick a load balancing algorithm and justify it under uneven load
- Make services stateless, and know exactly where the state went
- Handle instance failure with health checks instead of hope
- Do rough capacity math (QPS per instance, instance counts) on a whiteboard
Lessons
- 1When one server stops being enough9 minVertical limits, the horizontal move, and the single address that hides a fleet.
- 2Who gets the next request11 minRound robin, least connections, and hashing, raced against each other under uneven load.
- 3Where did the session go10 minWhy sticky sessions fight scaling, and how external session stores set services free.
- 4Instances die, users shouldn't notice11 minHealth checks, draining, retries, and why the load balancer itself can't be the weak point.
- 5Capacity math and interview framing9 minBack-of-envelope QPS estimates, when to bring up scaling, and the traps that sound smart.
Design with it after
The design library has full system design prompts on a whiteboard canvas with AI feedback. Every one of them gives you a place to apply this.
Open the design library