I am planning to build an ionic app that depends on a database, which would eventually have many data saved. I am wondering what is the best database available to have the app fully functioned? I am used to mySQL but I read it is not recommended to be used in Ionic. If there is a way to use mySQL without problems I would go for it. Google Firebase is an option I like but is it fully free if I want to use their database only without the other functionalities that they offer? What about MangoDB?