Which solution will provide the MOST fault tolerance?
Extend the Auto Scaling groups for the web tier and the application tier to deploy instances in Availability Zones in a second Region. Use an Aurora global database to deploy the database in the primary Region and the second Region. Use Amazon Route 53 health checks with a failover routing policy to the second Region.
Deploy the web tier and the application tier to a second Region. Add an Aurora PostgreSQL cross-Region Aurora Replica in the second Region. Use Amazon Route 53 health checks with a failover routing policy to the second Region. Promote the secondary to primary as needed.
Deploy the web tier and the application tier to a second Region. Create an Aurora PostgreSQL database in the second Region. Use AWS Database Migration Service (AWS DMS) to replicate the primary database to the second Region. Use Amazon Route 53 health checks with a failover routing policy to the second Region.
Deploy the web tier and the application tier to a second Region. Use an Amazon Aurora global database to deploy the database in the primary Region and the second Region. Use Amazon Route 53 health checks with a failover routing policy to the second Region. Promote the secondary to primary as needed.
Explanations:
While this option extends the Auto Scaling groups and uses Route 53 for failover, it does not utilize an Aurora global database, which is essential for cross-region replication and fault tolerance. The primary database remains in one region, creating a potential single point of failure.
This option proposes deploying a cross-Region Aurora Replica, but it does not mention using an Aurora global database, which would allow for seamless global deployment and fault tolerance. Additionally, promoting the replica to primary is manual and introduces potential downtime.
Although it suggests using AWS DMS for replication, this approach does not provide the level of fault tolerance needed for a global architecture. Creating a new Aurora database in the second Region means there is no built-in global failover capability, and AWS DMS is not designed for real-time replication.
This option uses an Aurora global database that allows for automatic cross-region replication and fault tolerance. It ensures that both Regions are synchronized, and if one fails, traffic can be rerouted to the other Region with minimal downtime using Route 53 health checks and failover routing.
I systematize that the answer is:
Deploy the web tier and the application tier to a second Region. Use an Amazon Aurora global database to deploy the database in the primary Region and the second Region. Use Amazon Route 53 health checks with a failover routing policy to the second Region. Promote the secondary to primary as needed.