How do I generate and store the state parameter for OAuth?

https://authorization-server.com/oauth/authorize
?client_id=a17c21ed
&response_type=code
&state=5ca75bd30
&redirect_uri=https%3A%2F%2Fexample-app.com%2Fauth
&scope=photos

The above is a standard format for OAuth authorization URL, and how do I generate and store the state parameter? I understand that you can encode information inside for redirect purposes and it's also for CSRF prevention, but does this mean I need to have a column in my database to store the state? Do I need to invalidate it after 30 mins to keep it "unguessable"? It seems very overkill, and I am utterly confused as to what's a good way to do this.