What is Scalability?
Scalability is a system's ability to handle growing amounts of users, data or transactions by adding resources, without a rewrite or a drop in performance. Systems can scale vertically (a bigger server) or horizontally (more servers sharing the load), and good architecture makes the second option practical.
Why it matters for your business
A scalable product can absorb growth, seasonal peaks and new markets without emergency rebuilds, which keeps infrastructure costs proportional to demand.
A ticketing platform runs its web tier in containers that add instances automatically when a popular event goes on sale, then scale back down once demand drops.