Ask HN: Which DataBase is faster if number of rows are in Millions?

Hi, I am trying to create a web application, which will have following functionality:

-> Crawl PR, Alexa, Backlinks, Page speed, etc. regularly and will store them into data base.

-> Generate history graph out of the stored data.

I will be tracking this things for all the domain names requested by the users. For a start I am planning to crawl data for Top 0.1 Million domains present in Alexa.

So which database should i go for. If possible proper guidance for what kind of architecture should i use will also be helpful.

I am planning to use PHP and MySQL along with Digital Ocean basic plan with Ubuntu OS for this.

Note: I am fresh CS grad and probably going to debut into the Tech StartUp world with this application.

Thanks, Vivek