I'm with the guys claiming premature optimization.
I think you've been duped by the legion of NoSQL evangelists into thinking RDBMS are old, slow and obsolete and if you put a few thousand rows into a few tables they'll bog down and take minutes to query it. Here's a spoiler: they're wrong. I think you'd be amazed just how robust and fast Postgres, MySQL and MS SQL can be if configured and used correctly.
The question NoSQL actually answers is "would you sacrifice atomicity and some consistency for a much higher data throughput?" I work on projects that have to manage sizable chunks of data every day and in my experience NoSQL is only an option after you've exhausted all other avenues. If you've designed a bulletproof database schema, optimized all your queries to the bone, created every possible index on every possible table, partitioned your database files and even thrown hardware at it and you still have issues, then NoSQL might be your salvation. Otherwise, stick to what everybody else is using.