FinTech Startup – Pros and Cons of Tech Stack?

I recently moved from a fortune 100 company to a FinTech startup. My background is mainly in infrastructure & security. However, I will be working very close to the development side.

I know this will be an open ended-question with a lot of answers around "it depends" but this is what I would like to know:

In the context of FinTech and startups, currently three people team (yours truly, one dev, and one CEO), zero-knowledge encryption, I will be working with the following tech stack - what are the pros and cons in your experience?

Webserver: NGINX Application Frontend: Node.js + Gulp + React/Flux Application Backend: Ruby on Rails Database: MySQL Infrastructure: AWS Configuration Management: Chef Code Repo: Github

Looking forward to your thoughtful advice!