Which scaling concept involves increasing capacity by adding more instances rather than upgrading existing ones?

• A. Vertical scaling
• B. Elasticity
• C. Horizontal scaling
• D. Mirror scaling

Answer: (C)

Increasing capacity by adding more instances rather than upgrading existing ones is horizontal scaling. The idea is to scale out by spinning up additional servers and distributing the incoming workload across them, often behind a load balancer. This approach lets you handle higher demand and improves fault tolerance, since if one instance fails, others continue serving traffic. Vertical scaling, by contrast, would mean upgrading the resources (CPU, memory) of a single machine, which doesn’t increase the number of instances. Elasticity describes the ability to automatically adjust resources in response to demand and can involve horizontal scaling, but the specific method described here is adding more instances. Mirror scaling isn’t a standard term in cloud discussions.