Firebase gives you functionality like analytics, databases, messaging and crash reporting so you can move quickly and focus on your users.
MySQL is an open-source relational database management system. It has established as a fast, stable and true multi-user, multi-threaded sql database server.
MongoDB is a cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with the schema. It is fast and developer-friendly. MongoDB supports field, range query, and regular-expression searches.