I have one small online sale business but I want to make it scalable at limited expense and so am looking out at various services which can help me make my business scalable.
I was looking into Amazon Web Services and it seems to be a viable option.
Are there any other ways for adding scalability to small online businesses ?
if possible, give more information, different online business may need different architecture.
Google app engine is also possible solution in beginning if easy to move there.
Up to a point, the cheapest thing to do is add more hardware and load balance it.
Scalability has to be well thought out. You should make sure your current architecture is designed to scale. Just adding more hardware is not a good solution. If you think your current implementation performs well and you do not need to tune it to respond faster or handle more traffic, then moving it to the cloud is a good idea so that adding more hardware is easy.
If thats not the case, then you should concentrate on things like DB tuning, caching (maybe use memcached and akamai) and performance optimization before you start thinking about porting it to some other technology.
A good starting point is to think about your average response times and how many requests your system can handle per second.
Most important for good scalability is architecture and implementation of the application to be scaled (run).
On your servers scaling relational database would be way more expensive than adding more application servers. On cloud the database back-end is limited. (Has less features than today's relational databases.)
So first thing to ensure to be scalable is: let the architecture of your application to use database at possible minimum and allows to have multiple application servers where maximum of the processing is done.
In web applications you can use javascript on your pages so the client's browsers make less requests and simpler requests to your server.
Another way said more servers is less expensive than single super-machine. And whatever you can use more servers is given by architecture of your application.
Caching can help to any application.