Exam Professional Cloud Architect topic 1 question 82 discussion

As per google documentation(https://cloud.google.com/solutions/scalable-and-resilient-apps) answer is C. C: A well-designed application should scale seamlessly as demand increases and decreases, and be resilient enough to withstand the loss of one or more compute resources. Resilience: designed to withstand the unexpected A highly-available, or resilient, application is one that continues to function despite expected or unexpected failures of components in the system. If a single instance fails or an entire zone experiences a problem, a resilient application remains fault tolerant—continuing to function and repairing itself automatically if necessary. Because stateful information isn’t stored on any single instance, the loss of an instance—or even an entire zone—should not impact the application’s performance.

Since the question is asking to do a resilience testing, I prefer C.

D. is not correct as this tests the resilience of the database (Cloud SQL) but not necessarily the authentication layer. The authentication layer might have separate components or dependencies that need to be tested under failure conditions.

Agree with C

Option C, which involves scheduling a disaster simulation exercise to shut off all VMs in a zone, is indeed a strong choice for resilience testing. This approach helps you understand how your application behaves under failure conditions and ensures that your system can handle unexpected disruptions. However, Option D is also highly relevant. Configuring a read replica for your Cloud SQL instance in a different zone and manually triggering a failover while monitoring KPIs for your REST API directly tests the resilience of your database layer. This can provide valuable insights into the failover process and the impact on your application’s performance and availability. Both options have their merits, but if the primary goal is to test the resilience of the authentication layer specifically, Option D might be more targeted and effective.

C is correct. It is not D because you are not designing system, your goal is testing existed system

Chaos testing

I choose Answer C https://cloud.google.com/sql/docs/mysql/replication This URL states "Read replicas are read-only; you cannot write to them. The read replica processes queries, read requests, and analytics traffic, thus reducing the load on the primary instance." "Note: Read replicas do not provide failover capability. To provide failover capability for an instance, see Configuring an instance for high availability." "As a best practice, put read replicas in a different zone than the primary instance when you use HA on your primary instance. This practice ensures that read replicas continue to operate when the zone that contains the primary instance has an outage. See the Overview of high availability for more information."

Testing Database Resilience: By setting up a read replica in a different zone and triggering a manual failover, you simulate a failure of the primary database. This allows you to assess how well your authentication layer and the overall application cope with the loss of the primary database. Monitoring Performance and Availability: During the failover, monitoring key performance indicators (KPIs) for your REST API will give you insights into how the application's performance and availability are impacted. This helps in identifying potential bottlenecks and areas for improvement in your resilience strategy. Ensuring Data Continuity: A read replica ensures data continuity and minimizes downtime, which is critical for an authentication system. The replica will take over as the primary database during the failover, ensuring that the authentication service remains functional.

D is okay

Authentication layer resiliency can be covered as part of overall application resiliency testing. Option C is asking to use read replica which is not useful in case of testing resiliency in case of failure

Read replicas do not provide failover capability. https://cloud.google.com/sql/docs/mysql/replication#read-replicas

It is c

Read replica do not provide failover capability https://cloud.google.com/sql/docs/mysql/replication#:~:text=Note%3A%20Read%20replicas%20do%20not,HA%20on%20your%20primary%20instance.

C is the good choice

I choose C. I don't say D because the REST API read and WRITE in the database, if you create a READ replica in Cloud SQL, the REST API will not have the possibility of write in the database. The answer D doesn't mention anything about promote the read replica to master.

C is good