is having millions of tables and millions of rows within them a common practice in MySQL database design?

Question

I am doing database design for an upcoming web app, and I was wondering from anybody profusely using mysql in their current web apps if this sort of design is efficient for

Answer 1

Millions of rows is perfectly normal usage, and can respond quickly if properly optimized and indexed.

Millions of tables is an indication that you've made a major goof in how you've architected your application. Millions of rows times millions of tables times 80,000 users means what, 80 quadrillion records? I strongly doubt you have that much data.