Handling Real Time data

Hi guys so I am thinking of building an application where a user can grab tweets in real time from their favourite users and display it on a board. I know I can use socket io to get the tweets in real time, but I am not sure how real time data is handled in databases, any one have any pointers? Also after a user has seen a tweet on their board is it best to delete? I tried thinking about how facebook's news feed works, they seem to store old posts in the news feed.