Scalability (scalability) is a characteristic of a system or software that indicates its ability to effectively increase or decrease its performance and resources in response to changing tasks or workloads. The main idea is that the system can adapt to growing loads or data volumes without losing performance or service quality. Scalability can be vertical or horizontal.

Includes increasing power or resources at the existing level of hardware. For example, adding new processors or memory to an existing server.

Includes adding new elements or nodes to the system. For example, distributed systems that can easily scale by adding new servers to a cluster.

Scalability is important for various fields of information technology, including web services, databases, applications, cloud solutions, etc. The ability to scale allows for efficient resource utilization while ensuring optimal performance and the system's response to changes in the environment. Do not confuse with High Availability (висока доступність).