Which approach will achieve this goal?
Launch large EC2 instances in the same Availability Zone
Spread EC2 instances across more than one security group
Spread EC2 instances across more than one Availability Zone.
Use an Amazon Machine Image (AMI) from AWS Marketplace.
Explanations:
Launching large EC2 instances in the same Availability Zone creates a single point of failure. If that Availability Zone experiences issues, all instances will be affected, reducing reliability.
Spreading EC2 instances across more than one security group does not inherently enhance reliability. Security groups control access but do not provide redundancy or failover capabilities.
Spreading EC2 instances across more than one Availability Zone increases reliability. If one Availability Zone goes down, instances in another zone can continue to operate, ensuring application availability.
Using an Amazon Machine Image (AMI) from AWS Marketplace does not guarantee reliability. The choice of AMI may affect performance and security, but it does not address redundancy or fault tolerance in the application architecture.
I rank that the answer is:
Spread EC2 instances across more than one Availability Zone.