From what you just said they're running for, at most, a few thousand people.
In terms of loads/numbers/etc. that's child's play and definitely not "huge applications". The kind of decisions he's talking about are for things with thousands of concurrent users per second, not per day.
That kind of stuff could be dealt with a single desktop computer running PHP and mysql. And you definitely don't need microservices.
In my experience, having worked in both enterprise and consumer startups, enterprise is shallow but broad with little need for any of the complicated stuff and more need to make the code really simple, obvious and uncomplex because it ends up dealing with so many different problems, while consumer scale is where you start needing to get a bit fancy purely because of scale, but it only deals with a couple of problems.
