Scalability
Definition.
Scalability: The property of a system to handle a growing amount of work by adding resources to the system.
In More Detail
Scalability is about what happens to cost and latency as load grows. A system that doubles its response time when traffic doubles does not scale, however fast it is when idle.
Vertical scaling — a bigger machine — is simpler and hits a ceiling. Horizontal scaling has no such ceiling but requires the application to be stateless, which is a design decision rather than something you add later. The database is usually the real constraint, and the first fix is almost always an index rather than another server.
In Practice
I design for scalability without over-building for it upfront — stateless API design, proper database indexing, and caching where it's actually needed, rather than premature infrastructure complexity a young project doesn't need yet.
Related Terms
Browse the full software development glossary, or see the frequently asked questions.
If you are working out whether this applies to your own project, the case studies show where it turned up in real builds, services lists what I take on, and pricing gives the starting figures.
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