If you are large enough, you will need an ops team to manage allowing your developers to write terraform and manage AWS costs already.
If you are small enough, you are not going to be truly affected by downtime. If you are just a little bigger, a single hot spare is going to be sufficient.
The place where you get dinged is heavy growth in personnel and bandwidth. You end up needing to solve CPU bound activities quicker because it hurts the whole system. You need to start thinking about sticky round robin load balancing and other fun pieces.
This is where the cloud can allow you to trade money for velocity. Eventually, though, you will need to pay up.
That said, the average SaaS can go a long way with a single server per product.
If you are small enough, you are not going to be truly affected by downtime. If you are just a little bigger, a single hot spare is going to be sufficient.
The place where you get dinged is heavy growth in personnel and bandwidth. You end up needing to solve CPU bound activities quicker because it hurts the whole system. You need to start thinking about sticky round robin load balancing and other fun pieces.
This is where the cloud can allow you to trade money for velocity. Eventually, though, you will need to pay up.
That said, the average SaaS can go a long way with a single server per product.