What is a Multi-AZ deployment, and how does it enhance fault tolerance?

Difficulty: 5/10

High Availability, Fault Tolerance, AWS EC2

Multi-AZ Deployments

A Multi-AZ deployment involves distributing your EC2 instances across multiple physically separated data centers (Availability Zones) within the same AWS Region. Each AZ is designed to be isolated from failures in other AZs, providing independent power, cooling, and network connectivity.

Fault Tolerance Benefits

1
Disaster Recovery: If one AZ goes offline, instances in other AZs continue to serve traffic.
2
Continuous Availability: ELB automatically detects the AZ failure and shifts traffic to remaining healthy instances.
3
Reduced Blast Radius: Faults, such as power or network connectivity issues, are contained within a single AZ.

Scenario Questions

0-2 years experience

2-5 years experience

1You notice that after a recent AZ outage, your application still experiences errors even though the EC2 instances were in a Multi‑AZ Auto Scaling group. What could be causing this and how would you debug it?

Follow-up Questions