Why is it a bad idea to use Session to store state in high traffic websites?

Question

I am watching the ASP.NET learn videos on asp.net/learn. In this tutorial, they are building a quiz engine. At one point, the narrator explains that we are going to use the Session object to maintain the state between each page (each page contains a question and four answers). He says that "since this is a low traffic website" it is okay to use Session and that he doesn't have the time to implement a more sophisticated method.

I am just wondering what alternate method(s) is he hinting at? And why is session a bad choice for a high traffic website?

Answer 1

Storing data in a database, or in cookies or some other method that is not directly tying up web server memory.

In addition to load, session also raises issues with the ability to use farms since you would either need to synchronize the session across the farm, or make sessions sticky, which can impact scalability.

Answer 2

For alternatives you can read the article Nine Options for Managing Persistent User State in Your ASP.NET Application.

In the articles the author explains the pros and cons of each method.

From the summary:

ASP.NET provides many different ways to persist data between user requests. You can use the Application object, cookies, hidden fields, the Session or Cache objects, and lots of other methods. Deciding when to use each of these can sometimes be difficult. This article will introduce the aforementioned techniques and present some guidelines on when to use them. Although many of these techniques existed in classic ASP, best practices for when to use them have changed with the introduction of the .NET Framework. To persist data in ASP.NET, you'll have to adjust what you learned previously about handling state in ASP.