If I quote a paragraph from Wikipedia about Optimization:
In computer science, program optimization or software optimization is
the process of modifying a software system to make some aspect of it
work more efficiently or use fewer resources. In general, a computer
program may be optimized so that it executes more rapidly, or is
capable of operating with less memory storage or other resources, or
draw less power.
And about Scalabilty:
Application scalability refers to the improved performance of running
applications on a scaled-up version of the system.
What's the difference? They both end up improving the performance of the system. Are they the same, if so, why are their names different?
Best Answer
Optimization is the process of making existing something more efficient, while doing the same operations. This can mean take less processing time for the same operation. It could mean taking less memory. It could mean taking less disk space. Optimization sometimes involves making trade-offs, like using more memory in exchange for faster processing.
Making things scalable means doing more of the same things. Further, it means doing more of the same things in an efficient manner. Searching for some item in your pocket is quick and easy. Searching for that same item in your house is harder. Searching for that same item when it could be anywhere in the world is super hard. Scalability is how drastically that sort of thing gets harder. "More" or better scalability means that searching all over the world is relatively only a little harder than searching in your pocket.
Like optimization, scalability can have a variety of targets. Sometimes the scalability target is processing time, like the search example. Sometimes it is database size. Sometimes it is memory consumption. Sometimes it's as simple as being able to show more stuff on the screen without driving your users nuts.
So in short, optimization is the act of making a single operation more efficient. Making things scalable is making that operation capable of doing more in a more efficient way.
Or if you could think of how an operation behaves for a series of inputs as a curve: optimization is lowering one point of the curve; making something scalable is lowering the slope of the curve.