High availability design patterns in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Architecture

intermediate

Understanding Multi-AZ Deployment Benefits

Which of the following best describes the primary benefit of deploying an AWS RDS database instance in Multi-AZ mode?

A It reduces the cost by using spot instances in multiple zones.

B It increases the database read throughput by distributing read requests across zones.

C It automatically replicates data across multiple Availability Zones to improve fault tolerance.

D It enables automatic scaling of the database storage based on demand.

💡 Hint

Think about what Multi-AZ means for availability and data safety.

Multi-AZ deployments create a synchronous standby replica in a different Availability Zone. This setup improves fault tolerance by allowing automatic failover if the primary instance fails.

❓ service_behavior

intermediate

Load Balancer Behavior in High Availability

What is the expected behavior of an AWS Elastic Load Balancer (ELB) when one of its registered EC2 instances becomes unhealthy?

A The ELB redirects traffic to a backup ELB in another region.

B The ELB continues to send traffic to all instances regardless of health status.

C The ELB terminates the unhealthy instance automatically.

D The ELB stops sending traffic to the unhealthy instance and routes requests only to healthy instances.

💡 Hint

Consider how ELB ensures availability by managing traffic distribution.

ELB performs health checks and stops routing traffic to instances that fail health checks, ensuring only healthy instances receive traffic.

❓ security

advanced

Designing High Availability with Secure Access

You want to design a highly available web application on AWS that restricts access to backend databases only from application servers. Which combination of AWS features best achieves this?

A Place application servers in public subnets and databases in private subnets with security groups allowing traffic only from application servers.

B Place both application servers and databases in public subnets with open security groups.

C Place application servers in private subnets and databases in public subnets with no security groups.

D Place application servers and databases in the same public subnet with security groups allowing all traffic.

💡 Hint

Think about subnet types and security groups to restrict access.

Placing databases in private subnets protects them from direct internet access. Security groups restrict traffic to only allow application servers to connect, enhancing security and availability.

✅ Best Practice

advanced

Implementing Auto Scaling for High Availability

Which Auto Scaling group configuration best supports high availability for a web application across multiple Availability Zones?

A Configure the Auto Scaling group with a fixed number of instances and no scaling policies.

B Configure the Auto Scaling group to span multiple Availability Zones with a minimum number of instances in each zone.

C Configure the Auto Scaling group in a single Availability Zone with a high maximum instance count.

D Configure the Auto Scaling group to launch instances only on demand without health checks.

💡 Hint

Consider how spreading instances across zones improves availability.

Spanning multiple Availability Zones with minimum instances in each ensures the application remains available even if one zone fails.

🧠 Conceptual

expert

Analyzing Failover Behavior in Multi-Region Architectures

In a multi-region AWS architecture using Route 53 with health checks and failover routing policy, what happens when the primary region becomes unreachable?

A Route 53 automatically routes traffic to the secondary region after detecting the primary region is unhealthy.

B Route 53 continues routing traffic to the primary region regardless of health status.

C Route 53 routes traffic to both regions simultaneously to balance load.

D Route 53 disables DNS resolution until the primary region recovers.

💡 Hint

Think about how DNS failover works with health checks in Route 53.

Route 53 monitors the health of the primary region and automatically switches DNS responses to the secondary region if the primary is unhealthy, ensuring availability.