Scalability refers to:

Scalability specifically refers to the ability of a system to accommodate increases in capacity needs without requiring a complete redesign. This means that as the demand for resources grows—whether due to more users, increased data volume, or higher transaction rates—the system can expand to meet these demands seamlessly.

In cloud computing, scalability is a critical feature because it allows organizations to efficiently manage varying levels of workload. When a system is scalable, it can adapt autonomously without downtime or significant changes to its architecture, making it easier to respond to fluctuating business requirements. This helps organizations save time and resources, ensuring they are only using the necessary amount of resources at any given moment.

The other options focus on specific aspects of system performance or cost management but do not capture the broader definition of scalability itself. Maintaining performance during peak hours is related to performance optimization, reducing costs pertains to economic aspects, and improving security measures addresses the safety and integrity of applications—none of these encompass the core concept of scalability as effectively as the ability to accommodate increased capacity needs without redesign.