You're defining the term big data as "an amount of data that seems impressive to me". That's a pretty loose definition, and two people could have wildly differe

You're defining the term big data as "an amount of data that seems impressive to me". That's a pretty loose definition, and two people could have wildly different ideas. I prefer to define big data as "an amount of data that cannot fit on any one computer." Once you start using distributed systems, either with sharding, NoSQL, or similar tech, you're in big data territory. Going from one computer to two you greatly increase the complexity of the system.