Chapter 6: Scaling Your Infrastructure

1. No, it is not always the best choice because a multi-level application means more components to manage. If your application works well as a monolith, you can accept a short period of downtime and the traffic will not increase over time. You can also consider letting it run as it is.
2. In the multi-level approach used in this book, all software is in one ZIP file, instead in a microservices and more in the serverless approach it is broken in multiple parts. For example, in an e-commerce software (the software used to show the content to the users in one service), the part to manage the backend to place a new product is in one service, while the part to manage the payment is in another service, and so on. 
3. If you are not familiar with the service, it can be difficult. However, AWS is full of documentation...