Scalability is the ability of a system to handle increasing workloads by adding resources. A scalable system can grow in capacity without redesigning major components. Scalability can be vertical (adding more power to a single instance) or horizontal (adding more instances behind a load balancer).
Why it matters
Scalable designs ensure that applications remain responsive as traffic, data, or complexity grows. Scalability influences cost efficiency, performance, and long-term maintainability.
Examples
Auto-scaling containers during traffic spikes or moving from a single-server architecture to distributed microservices. Lessons like Vertical and Horizontal Scaling explain scaling strategies.