Vertical scalability, also known as "scaling up," refers to the ability to increase the capacity of a single server or machine. This can be achieved by adding more resources, such as CPU, RAM, or storage, to handle increased workloads. Vertical scalability is often simpler to implement since it involves upgrading existing hardware rather than adding new machines. However, there are limits to vertical scalability, as a single server can only be upgraded to a certain extent. Once these limits are reached, organizations may need to consider horizontal scalability, which involves adding more servers or machines to distribute the load. This approach can provide greater flexibility and resilience in handling large-scale applications.