Hi guys 
I have a project for which I need a database that is suitable for storing chat messages and posts where the user specifies a time at the post how long it should be online. The same for the chat function.
I hope someone can give me some tips.
Thanks
Any database is dynamic, that’s the point, you can add data and query data and delete data. So like a relational DB you might have a table for posts with columns for the post id, user id associated with it, the post text, and a time for when it should be deleted. Then you either add triggers using the database system itself for when that time is hit & to delete the post. Or you have some logic outside the database that checks every so often and tells the database to delete expired posts.