What is the recommended number of Availability Zones to start with per Region as a best practice?

When designing a resilient and highly available architecture in AWS, it is considered a best practice to start with at least two Availability Zones per Region. This approach takes advantage of the fault tolerance provided by multiple, separate physical locations within a region, ensuring that your applications are not impacted by issues that occur in a single zone.

By using two Availability Zones, you can implement a setup that features redundancy and can withstand the failure of one zone while still serving the application seamlessly from the other zone. This setup allows for improved performance through load balancing and increases the overall availability and reliability of your services.

Additionally, having two Availability Zones enables the deployment of a disaster recovery strategy. In the event that one zone experiences an outage, the systems in the second zone can take over, minimizing downtime and maintaining service continuity.

In contrast, choosing just one Availability Zone would negate these benefits, as a failure in that single zone would directly result in an outage of the services hosted there. While using more than two zones, such as three or four, can provide even greater levels of redundancy and availability, two is often viewed as the practical minimum for building a robust architecture in AWS.