An application is scalable when it can handle an increasing number of users or requests without crashing or slowing down.
For example, imagine an e-commerce website that experiences a surge in traffic during a holiday sale. If the app is scalable, it can handle the increased number of visitors without any issues, ensuring a smooth shopping experience for all users. If the application is built without considering scalability, it is likely to crash or experience degraded performance.
One common approach to achieving scalability is through horizontal scaling, also known as scaling out, which involves adding more machines or nodes to your system. This can be done using load balancers to distribute incoming requests across multiple servers, ensuring that no single server becomes overwhelmed. Another approach is vertical scaling, or scaling up, which involves adding more resources, such as CPU, memory, or storage, to a single machine. Both approaches have their pros and cons, and the choice between them depends on the specific requirements and constraints of the system.