[doojin]

If you genuinely want to become a software entrepreneur for the rest of your life, you just have to pay the price of learning horizontal scalability once and reuse your knowledge for the rest of your life. Thus, my opinion only applies to dedicated software entrepreneurs.

In my experience, horizontal scalability isn't difficult if you are actually a software engineer. Actually, I wouldn't hire any programmer who can't understand horizontal scalability quickly. I'm saying this as someone who's not particularly smart.

You don't have to implement everything in the early stages, but you have to know distributed design and implement some of it so that your software isn't hindered severely later when you actually need to implement more scalability techniques.

Definitely, learn distributed design, and implement it gradually over time. Don't paint yourself into a corner by implementing things that can't be scaled later.

For example, you don't have to deploy a load balancer from the beginning, but make sure your software can work with a load balancer later. That means stateless design. Stateful design can't work with a load balancer.