Kudos to Martin Casado of a16z on great explanation of why startups need to hire a VP Engineering early, rather than waiting for the founders to be overwhelmed by the organizational challenges of scale.  

The key insight here is that a VP of Engineering builds the process and the culture of a company's engineering org.  How?  The right VP will buffer the team from the daily fires within the business (ahem, the CEO), providing consistent leadership that will attract talent, retain talent, and deliver great product on time. Organizationally, the right VP also permits the CTO to pivot to evangelism, board interactions, and forward-looking tech planning that will keep the product advancing. 

Highly suggest reading the whole article!