Architecting on AWS Certification Architecting on AWS Certification High Availability & Fault Tolerance 2 — Questions and Answers
Question 1: Which AWS architectural principle recommends designing systems assuming that components will fail?
- Design for performance
- Design for failure (Correct answer)
- Design for cost
- Design for simplicity
Correct answer: Design for failure
AWS Well-Architected Framework's reliability pillar advises designing systems to expect and automatically recover from component failures.
Question 2: An application uses DynamoDB and must remain available if an Availability Zone fails. Which DynamoDB feature handles this automatically?
- DynamoDB Streams
- DynamoDB Accelerator (DAX)
- DynamoDB built-in multi-AZ replication (Correct answer)
- DynamoDB Global Tables
Correct answer: DynamoDB built-in multi-AZ replication
DynamoDB automatically replicates data across three Availability Zones in a Region, providing built-in high availability with no additional configuration.
Question 3: Which AWS service can be used to implement a dead-letter queue to capture messages that repeatedly fail processing in an SQS-based architecture?
- Amazon SNS
- Amazon SQS itself (Correct answer)
- Amazon Kinesis
- Amazon EventBridge
Correct answer: Amazon SQS itself
SQS supports dead-letter queues, which are separate SQS queues where messages that exceed the maxReceiveCount are automatically moved for later inspection.
Question 4: An architect must ensure an EC2-based application recovers automatically after an instance failure with the least operational effort. What is the best approach?
- Use EC2 user data to relaunch the instance
- Place the instance in an Auto Scaling group with min=1 (Correct answer)
- Create a CloudWatch alarm that sends an email
- Use AWS Backup to restore the instance
Correct answer: Place the instance in an Auto Scaling group with min=1
An Auto Scaling group with minimum capacity of 1 automatically launches a replacement instance if the existing one terminates or fails a health check.
Question 5: Which ELB listener rule action allows an Application Load Balancer to return a static error page when the backend targets are all unhealthy?
- Redirect action
- Fixed-response action (Correct answer)
- Forward action
- Authenticate action
Correct answer: Fixed-response action
The ALB fixed-response action returns a custom HTTP response (status code + body) directly from the load balancer without routing to any target.
Question 6: What is the purpose of an Amazon Aurora cluster's reader endpoint?
- It routes writes to the primary instance only
- It load-balances read traffic across all Aurora replicas (Correct answer)
- It connects to the cluster from outside the VPC
- It provides a static IP for the cluster
Correct answer: It load-balances read traffic across all Aurora replicas
The Aurora reader endpoint automatically distributes read connections across all available Aurora Replicas, reducing load on the primary writer instance.
Architecting on AWS Certification Architecting on AWS Certification High Availability & Fault Tolerance 2
Which AWS architectural principle recommends designing systems assuming that components will fail?