Explain the concept of High Availability in the context of EC2 instances.

Difficulty: 5/10

Auto Scaling, Elastic Load Balancing, Multi-AZ

High Availability (HA) for EC2

High Availability refers to the ability of an application to remain operational, even during component failures or outages. In the context of EC2, this means architecting your infrastructure to survive the failure of an instance, a rack, or even an entire Availability Zone (AZ).

Key Strategies for HA

1
Redundancy: Running multiple instances across different AZs.
2
Health Checks: Automatically detecting and replacing unhealthy instances via Auto Scaling.
3
Load Balancing: Using ELB to distribute traffic across healthy, available instances.
4
Data Replication: Ensuring data (like EBS snapshots or database replicas) is synchronized across AZs.

Scenario Questions

0-2 years experience

2-5 years experience

1Your service runs behind an Application Load Balancer across two Auto Scaling groups, but you notice occasional downtime during scaling events. What could be causing the HA issue and how would you debug it?

Follow-up Questions