We are working on a web application which will be having 20,000+ end users. We have to build up the login module for this application. Please suggest the best ways to implement the login module so that there are no performance issues during high load.
What are the best practices we need to follow for the same?
Also, how to control the concurrency and transactions for the same?
I'll point out that a login module is unlikely to be a performance bottleneck. If I login once for every 10 normal actions I perform, that means that 1/11th of your traffic at any given time will be due to login requests. Most sites I use, it's even more skewed than that, like one login for every 20 or 100 or 1000 other actions.
So don't worry about login performance unless and until it becomes a problem. First make it work, and if you're going to look at performance, look at it for stuff your users do once they're logged in, as that's likely to be called much more often.