performance – What is a starting point for finding the fastest databases for inserting and querying millions of rows per second?

I am a database noob. I work on an application that reads a real-time source of data that generates records on the order of a million per second (or more) and stores them in a homegrown database. A UI front end queries that database to display the real-time data in various ways, including the current state. Querying needs to be as fast or faster than real-time. The data itself is processed when read from the source and then stored in the database, barely changing. The application’s database is really fast at inserting and simple queries, but fails at basic features a “real” database can do (like say, sorting) which are limits we are currently hitting. I realize there are countless factors that decide what kind of database is best to use, but if I were concentrating on raw performance which databases would be a good place to start looking?