CodeIgniter - Appropriate for medium scale

I'm on my second (very large) project with CI, among the dozen or so smaller ones.

My first project manages some 2 million requests daily, handles a multi million dollar business both front and back end with a few thousand orders daily.

My current project manages a SaaS with hundreds of clients who use it as a POS system at thousands of locations across the nation. We have over 50,000 concurrent users at any given time. (we also have hella servers, backup servers, routers and can spin up more on demand) We handle POS terminal CC transactions (as well as a slew of other payments), reservations, services, POS items, cash drawers, etc.

Both on CI, the first using a jQuery frontend, the second ReactJs.

It can handle pretty much whatever you throw at it.