Modern hardware is fast, if you cannot fit more than 100 users (not even 100 concurrent users) on a single $50/month server, you're doing something very very wrong.

Even repurposed 10 years old fairphone[1] can handle more than that.

[1]: https://far.computer

1) His user numbers are off by an order of magnitude at least, as other comments have mentioned. Even a VM/VPS should handle more, and a modern bare-metal server will do way more than the quoted numbers.

2) Autoscaling is a solution to the self-inflicted problem of insanely-high cloud prices, which cloud providers love because implementing it requires more reliance on proprietary vendor-specific APIs. The actual solution is a handful of modern bare-metal servers at strategic locations which allow you to cover your worst-case expected load while being cheaper than the lowest expected load on a cloud. Upside: lower prices & complexity. Downside: say goodbye to your AWS ReInvent invite.

3) Microservices. Apparently redeploying stateless appservers is a problem (despite the autoscaling part doing exactly this in response to load spikes which he's fine with), and his solution is to introduce 100x the management overhead and points of failure? The argument about scaling separate features differently doesn't make sense either - unless your code is literally so big it can't all fit in one server, there is no problem having every server be able to serve all types of requests, and as a bonus you no longer have to predict the expected load on a per-feature basis. A monolith's individual features can still talk to separate databases just fine.