Reliability pillar principles in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Recovery Time Objective (RTO)

What does the Recovery Time Objective (RTO) represent in the context of the Reliability pillar?

A The maximum acceptable time to restore a service after a failure

B The number of redundant servers required for fault tolerance

C The total uptime percentage of a service over a year

D The amount of data loss allowed during a failure

💡 Hint

Think about how quickly you want your service back after it stops working.

RTO is the target time set for recovering a service after an outage to minimize downtime.

❓ Architecture

intermediate

Designing for Fault Tolerance

You want to design a web application that remains available even if one server fails. Which AWS service combination best supports this goal?

A Use multiple EC2 instances behind an Elastic Load Balancer (ELB)

B Use an S3 bucket to host the application

C Use a single Lambda function triggered by API Gateway

D Use a single EC2 instance with EBS volume

💡 Hint

Think about spreading traffic across multiple servers to avoid single points of failure.

Multiple EC2 instances behind an ELB distribute traffic and provide fault tolerance if one instance fails.

❓ security

advanced

Impact of Security on Reliability

Which security practice directly improves the reliability of a cloud service?

A Using complex passwords without multi-factor authentication

B Allowing open inbound traffic on all ports for easy access

C Implementing least privilege access to reduce accidental changes

D Disabling logging to improve performance

💡 Hint

Consider how limiting access can prevent mistakes that cause outages.

Least privilege access limits who can change resources, reducing accidental disruptions and improving reliability.

❓ service_behavior

advanced

Behavior of Auto Scaling in Reliability

What happens when an Auto Scaling group detects an unhealthy instance?

A It sends an alert but takes no action automatically

B It pauses all traffic until the instance recovers

C It duplicates the unhealthy instance to handle load

D It immediately terminates the unhealthy instance and launches a new one

💡 Hint

Think about how Auto Scaling maintains healthy resources automatically.

Auto Scaling replaces unhealthy instances automatically to maintain service availability and reliability.

✅ Best Practice

expert

Implementing Multi-AZ Deployments for High Availability

You want to ensure your database remains available even if one Availability Zone (AZ) fails. Which AWS feature should you use?

A Deploy multiple RDS instances in different regions without replication

B Deploy an RDS Multi-AZ configuration with synchronous replication

C Deploy a single RDS instance in one AZ with automated backups

D Use a single EC2 instance with a local database

💡 Hint

Think about synchronous replication across AZs for automatic failover.

RDS Multi-AZ deployments replicate data synchronously to a standby instance in another AZ, providing high availability and failover support.