The Basics of Express Sessions and Why To Use it.

When managing a user’s data you would like to keep their data, so you can give each user a unique experience. This is one of last few concepts you would need to understand until building a full blown application .

What do you use?

They are 3 options express-session, client-sessions, and cookie session. If they are any that I missed please comment. We will be using express-session. Here is the resources for these three.


Cookie Session


Look at it or go on! Sessions store user data when accessing and browsing application. Allows applications to store state. For Example if I login, how the server remembers my activity is by my session.

What are the ways of storing user data?

The easiest and simplest is storing in the application memory. In a form of a cookie. In memory cache. And a database store.

Why store data in application memory?

It is easiest, and is preferred for beginners to start with. Data for application runtime. If server stopped or there issues with server data is lost. When it comes to production it is a bad idea, because the application memory eventually runs out, there is a memory leak. Therefore giving unauthorized users the ability to access user data. In production it IS NOT A GOOD IDEA.

Why store data in a cookie?

A piece of data between server and browser for a unique user. Sent a period time with a expiration date. Manipulate cookie if needs and sends back to browser.

This is when express-sessions comes in?

This is when express-session does work under the hood. It saves and retrieves data using a cookie. Cookies though are about 4KB in memory, and it would be a bad idea to store so many do to the fact it can cause bad performance, and if the encryption is found a unauthorized user can access their data.

Why store data in memory cache or cache?

Only small chunk is store in a form of a key-value pair. It contains a sessionId that is a unique id for the store. Removes risk of accessing data. It can be a pain to setup do to the fact you have to setup another server, might be a overkill for small applications, and there is no way of removing data unless removing all of cache. Use redis or connect-memcached for this functionality.

Final solution store data in a database.

Maps the sessionId as a primary key in a database. Slower because it is retrieving data via disk. Look at this for the databases used with express-sessions.

What are the best ways of storing data?

If needed store in cookie, memory cache, and store database is all a good solution, but each one has it issues. Protect user data using redis or connect-memcached, secure primary keys, and store data in database store.

Look at this article for more info.

and this one for an example.