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
Start the course- When one server stops being enough9 minVertical limits, the horizontal move, and the single address that hides a fleet.
- Who gets the next request11 minRound robin, least connections, and hashing, raced against each other under uneven load.
- Where did the session go10 minWhy sticky sessions fight scaling, and how external session stores set services free.
- Instances die, users shouldn't notice11 minHealth checks, draining, retries, and why the load balancer itself can't be the weak point.
- Capacity math and interview framing9 minBack-of-envelope QPS estimates, when to bring up scaling, and the traps that sound smart.
The account is free and so is every lesson. It unlocks the courses and saves your progress.
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