Scalability and Performance
How systems stay fast while load grows tenfold: stateless design, load balancing, caching at every layer, and queues that absorb spikes. You then learn to measure latency honestly, find real bottlenecks, and plan capacity.
This domain is the engineering of speed under load. You learn the scaling mechanics first: stateless services, load balancers, and autoscaling. Then the two great load absorbers, caching and queues, and finally the measurement discipline: percentiles, bottleneck hunting, database tuning, and load testing before launch day finds the limit for you.