CD with 2 separate Azure web apps or 1 web app scaled out to 2 instances?

Question

For a new project (Sitecore PaaS) I'm wondering if it would be better to

1. Run the CD with two separate web apps (both single instance) implementing the zero-downtime deployment myself in the deployment process. Using a traffic manager, etc.
2. Have just one web app scaled out to 2 instances and then use deployment slots to have zero downtime deployments.

I've some experience with the first approach and I really like the fact that you are in full control of both specific web apps that are responsible for Content Delivery (being able to resolve a page on a specific web app by using a web app specific hostname). But after some googling, I get the idea that most Sitecore PaaS implementations are set up with the second option.

I couldn't find any Sitecore recommendations about this topic.

Answer 1

Option 2 is the way to go in an Azure PaaS architecture. If you are not a fan of swapping deployment slots, you can use traffic redirection on the different slots. (Also known as `Testing in production") This approach of deploying is closer to what you where doing in IaaS regarding traffic control. (More info on this subject: http://onelittlespark.bartverdonck.be/testing-in-production/)

Regarding option 1: Since the traffic manager operates on IP level (DNS resolving), you have only limited control over the traffic. You might even experience custom domain binding issues when trying to add the same URL on 2 different web apps in the same datacenter.