Auto Scaling
In plain terms
Automatically adding or removing servers based on current demand.
Going deeper
Auto scaling watches metrics like CPU or traffic and spins resources up during spikes and down when quiet, balancing performance and cost without manual intervention.
Under the hood
Driven by target metrics or schedules; needs sensible min/max bounds, cooldowns to avoid flapping, and stateless apps so instances are interchangeable.
Examples
AWS Auto Scaling Groups, Kubernetes Horizontal Pod Autoscaler, CPU/queue-depth triggers.
Think of it like...
Like a store that automatically opens more checkout lanes when lines grow and closes them when it's quiet.