I am developing a web application using django, postgreSQL, html5 and javascript. The application is javacript intensive and is both read/write intensive. What are some common bottlenecks? What are some things to keep in mind when designing a web application that scales well? What are some tips to improve performance?
Thanks!
You may take a look at http://ilian.i-n-i.org/tag/cache/ there are three articles about caching and how it will help your website.
As for the scales well… are you sure that your application needs it?
Do not get me wring, it is awesome to have multiple database servers, CDN, load balancers etc. but do you really need it? If you are starting a new project you should focus on providing a stable features more than optimizing it for a million hits per day cause you are probably not going to make them(at least in the beginning).
Start with caching, it is easy to implement and effective if it is correctly used. When your visitors get so much that you reach the bottle necks think for them then but not earlier.
The above does not mean that you should write the slowest code that is possible. It only means that the need for extreme scalability comes when you have working application and that if you waste 1 year and a ton gold to build it probably you will miss the moment.