Resilience Testing for Regional MIG with Cloud SQL

Ensuring the reliability of solutions in production (e.g., chaos engineering, penetration testing, and load testing) Designing a solution infrastructure that meets technical requirements.

Your customer wants to do resilience testing of their authentication layer. This consists of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance. What should you do?

Engage with a security company to run web scrapers that look your for usersג€™ authentication data om malicious websites and notify you if any is found.
Deploy intrusion detection software to your virtual machines to detect and log unauthorized access.
Schedule a disaster simulation exercise during which you can shut off all VMs in a zone to see how your application behaves. Correct Answer
Configure a read replica for your Cloud SQL instance in a different zone than the master, and then manually trigger a failover while monitoring KPIs for our REST API.

Answer Correct answer: C — Shut off all VMs in a zone during a disaster simulation to verify the regional managed instance group's resilience and observe how the REST API behaves under compute resource loss.

Community Insight

The question tests understanding of resilience testing versus security monitoring or database replication, with the common trap being to choose the database failover option when read replicas in Cloud SQL do not provide failover capability.

This question tests how to properly perform resilience testing on an authentication layer composed of a regional managed instance group and a Cloud SQL database. The correct approach is to simulate a zone-level failure by shutting down all VMs in one zone, which directly validates whether the regional MIG can withstand and recover from compute resource loss.

Many learners choose option D, believing that manually triggering a Cloud SQL read replica failover constitutes resilience testing. However, Google Cloud documentation explicitly states that read replicas do not provide failover capability—they are designed for read scaling, not automatic or manual HA failover to replace a primary instance.

Community Discussion (132 comments)

Pime13 👍 1 Selected: C

Regional MIG Resilience: A regional managed instance group is designed to survive zonal outages by automatically redistributing or recreating instances in healthy zones. Shutting off all VMs in a zone is a standard "chaos engineering" practice to validate that your application remains available and that your autoscaling/self-healing configurations work as expected under stress. Google-Recommended Practice: Google explicitly provides scripts and metadata methods to simulate zonal failures for regional MIGs to test if they are correctly overprovisioned and capable of surviving such events. .

Pime13 👍 1

Targeting the Architecture: Since your application uses a regional MIG, testing its ability to handle a full zone being offline is the most comprehensive way to validate the "resilience" of the authentication layer. not D: While this tests the database's High Availability (HA) failover, a regional managed instance group is primarily an infrastructure-level tool. Testing the VMs themselves (Option C) provides a broader validation of the entire application stack's ability to reroute traffic and maintain service during a disaster. In a true resilience test, you want to see how the application handles the combined loss of compute and potential database reconnects.

JoseCloudEng1994 👍 1

Resilience is a broader concept. It is the ability of a system to not only survive a failure but also to adapt to and recover quickly from adverse conditions or disruptions. It's about how the system handles unforeseen failures and operates even in a degraded state. Key Question: Can the system recover from failure? How it's achieved: Through strategies like self-healing, graceful degradation, and a robust disaster recovery plan. A resilient system may experience a temporary dip in performance, but it can quickly bounce back to an effective operational state.

DM____1111 👍 1 Selected: D

This approach directly tests how your application's authentication layer behaves when its database experiences a failover event, which is crucial for resilience. C is not correct because while shutting off all VMs in a zone is a valid and comprehensive disaster recovery test for a full zonal outage, it's a very broad test. The question specifically asks about testing the authentication layer's resilience and its reliance on Cloud SQL. Directly testing the Cloud SQL failover is more focused and efficient for this particular goal.

f3e7abb 👍 1 Selected: D

Resilience in this case means at least be able to support a failure of a zone, so considering that the MIG is regional, so it can withstand a zonal failure, the only other thing is to have a failover strategy for Cloud SQL and triggering it.

MrAZ105 👍 1 Selected: D

D is correct

khadar2001 👍 1 Selected: B

The requirement is on authentication layer so selected answer B. This is confirmed from GCP Practice exam.

david_tay 👍 1 Selected: D

answer is D, check in Gemini to understand why.

Ekramy_Elnaggar 👍 2 Selected: 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.

nareshthumma 👍 2

Agree with C

wooyourdaddy 👍 2 Selected: D

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.

hitmax87 👍 4 Selected: C

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

666Amitava666 👍 4 Selected: C

Chaos testing

activist 👍 3

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."

santoshchauhan 👍 1 Selected: D

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.

Rehamss 👍 1 Selected: D

D is okay

Teckexam 👍 3 Selected: C

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

practice_sample 👍 3 Selected: C

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

didek1986 👍 2 Selected: C

It is c

Tamim321 👍 6 Selected: 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.

Roro_Brother 👍 2 Selected: C

C is the good choice

juliansierra 👍 6

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.

parthkulkarni998 👍 1

Exactly. Because in GCP a read replica cant be auto upgraded to become a master in case of failover. So basically the database will allow only READ operations and not WRITE operations. Basically leaving it non-functional

RuibinC 👍 2 Selected: C

C is good

Prakzz 👍 3 Selected: C

D can be correct if it's a Failover replica but it's a read replica and not have anything to do with resiliency. It's C

marcohol 👍 3 Selected: D

Option A is focused on external threat intelligence and is more suited to security testing rather than resilience testing. Option B is related to security monitoring, and while important, does not directly address resilience testing requirements. Option C simulates a zone failure scenario. This could provide insights into how the application behaves in a failure scenario, making it a valid resilience testing method. However, it does not specifically address the interaction with Cloud SQL. Option D directly addresses resilience testing involving a Cloud SQL instance by creating a read replica in a different zone and simulating a failover. This will allow you to assess the impact on your REST API and verify whether the authentication layer remains functional and available, even when the primary Cloud SQL instance is inaccessible.

parthkulkarni998 👍 1

I think answer should be C, because Read Replicas are there for improving scalability and not availability. So whenever, a node/zone goes down, a read replica wont auto transform to a master. For that you need a failover replica by enabling HA configuration in VMs.

ductrinh 👍 2

its quite tricky here resilient = chaos test. so with C, we have shut down all VMs in one zone to see how its it working on another zone( note that this is regional ) is my chose

piiizu 👍 2

The application was deployed to a managed Instance Group, it must have been configured with a load balancer, health check and AutoHealing. Turning off VMs would instantly bring up another instance as soon as the health checks fail, and traffic is automatically redirected to these instances. Therefore, the Answer is D.

didek1986 👍 1 Selected: D

d is correc

ChauHuuPhat 👍 3 Selected: D

This will test the ability of your authentication layer to continue to function even if one of the zones fails. By configuring a read replica in a different zone, you can ensure that there is always a copy of your data available. And, by manually triggering a failover, you can test how your application behaves when the primary instance is unavailable.

Sur_Nikki 👍 1

Resilience testing of their authentication layer means the testing of availability of service/application even when many of the instances fail in a particular location. That’s why. Disaster type of scenario is better where all VM instances becomes unavailable in a particular zone

salim_ 👍 2 Selected: C

C as it's definition of resilience testing. D is not correct at all as when disaster occurs you don't have time to "Configure a read replica for your Cloud SQL instance in a different zone than the master"

Hisayuki 👍 2 Selected: D

D is right

JC0926 👍 5 Selected: D

D. Configure a read replica for your Cloud SQL instance in a different zone than the master, and then manually trigger a failover while monitoring KPIs for our REST API. This option is the most suitable for resilience testing of the authentication layer. By configuring a read replica in a different zone than the master, you add redundancy to your system. Manually triggering a failover while monitoring KPIs for your REST API helps you observe how the system behaves during a failure and ensures that the authentication layer remains available and performs as expected during an outage or disaster.

taer 👍 2 Selected: C

vote for C

feholen210 👍 2 Selected: C

C is correct.

Hawik 👍 2 Selected: C

Should be C

Deb2293 👍 1 Selected: D

D is right

zeekerblade 👍 2 Selected: C

In the question, //This consists of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance. It means it consist of MIG, but does not imply it consists of Cloud SQL as well. Some argues that MIG is regional and don't need to be tested is definitely incorrect. there are many configurations may differs the behaviors and even cloud provider stated does not mean that we do not need to test it out.

JC0926 👍 1 Selected: D

Option D is a valid method of testing the resilience of the authentication layer. Configuring a read replica in a different zone allows for redundancy and failover capabilities in the event of a disaster. By manually triggering a failover and monitoring the KPIs for the REST API, the resilience of the authentication layer can be tested under realistic conditions.

telp 👍 1 Selected: D

D => instance group is alreay regional the point of failure is the cloud sql so need to test resilience

Deb2293 👍 3 Selected: D

Option D is right Option C is also incorrect because shutting off all VMs in a zone is not a realistic scenario for testing the resilience of the authentication layer, as it does not simulate a specific failure mode. Additionally, it may have unintended consequences on other parts of the application that rely on the same VMs.

Deb2293 👍 1

Option C is incorrect as it relies on using the bq command line tool to list jobs and job information, which may not be the most efficient or reliable way to get the information required. Additionally, it may require more manual effort to compile the data for each user.

omermahgoub 👍 6

The correct answer is D. Configure a read replica for your Cloud SQL instance in a different zone than the master, and then manually trigger a failover while monitoring KPIs for our REST API. Resilience testing is a process of evaluating the ability of a system to recover from failures or disruptions. In this case, the customer has an authentication layer consisting of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance. To perform resilience testing, one option would be to configure a read replica for the Cloud SQL instance in a different zone than the master. This would allow you to test the system's ability to recover from a failure or disruption in one zone. Then, you could manually trigger a failover while monitoring key performance indicators (KPIs) for the REST API, such as response times and error rates. This will allow you to see how the system behaves during a failover and identify any potential issues that need to be addressed.

Sur_Nikki 👍 1

Sorry, but I don't agree with your answer. I would like to move with C

omermahgoub 👍 4

Option A, engaging with a security company to run web scrapers looking for users' authentication data on malicious websites, is not related to resilience testing. Option B, deploying intrusion detection software to your virtual machines to detect and log unauthorized access, is a good practice for improving the security of your system, but it is not directly related to resilience testing. Option C, scheduling a disaster simulation exercise during which you can shut off all VMs in a zone to see how your application behaves, is a valid method of resilience testing, but it does not involve testing the system's ability to recover from a failure or disruption in one zone.

fiercedog 👍 4 Selected: D

Answer is D. App layer is covered by regional managed instance group. Database is the point of failure that needs to be addressed.

megumin 👍 2 Selected: C

C is ok

AzureDP900 👍 1

C is right - It correct way to test.

minmin2020 👍 2 Selected: C

C is the only option closer to testing resilience of the authentication layer A and B I cannot see how resilience of the authentication layer is tested D will only test SQL

DrishaS4 👍 3 Selected: C

So, C and D to consider. Resiliency definition: a highly-available, or resilient app is one that continues to function despite expected or unexpected failures of components in the system.

xinsong001 👍 3

The answer is C: Regarding the resilience test, they don't mean to test MIG autoscaling, which has been tested by Google. What they want to test is whether or not the request for authentication will be lost if the VM node suddenly crashed when it's sending API request

heretolearnazure 👍 3

yes chaos testing is industry standard

haroldbenites 👍 3

Go for C.

vincy2202 👍 2

Answer is C

mudot 👍 4 Selected: C

A & B - not resiliency testing D - tests only for SQL its C

joe2211 👍 2 Selected: C

vote C

MaxNRG 👍 4

C – schedule a disaster simulation exercise during which you can shut off all VMs in a zone to see how your app behaves. A, B – don’t test resilience at all, just security / authentication attacks. But, Q asks different – check if authentication works if some resources are down. So, C and D to consider. Resiliency definition: a highly-available, or resilient app is one that continues to function despite expected or unexpected failures of components in the system. D – says about Read Replica and trigger a failover. But, Read replicas neither provide High-Availability nor offer it; a master instance cannot failover to a read replica, and read replicas are unable to fail over in any way during outage. C – focuses on both aspects: resilience and authentication layer testing by shutting down FrontEnd VMs in the zone. Cloud SQL testing is OOO, since this is back-end / data layer.

MaxNRG 👍 3

HA Configuration of Cloud SQL – shows Failover example with Master and Read + Failover replica: https://cloud.google.com/sql/docs/mysql/high-availability Read also about Building scalable and Resilient Apps: https://cloud.google.com/architecture/scalable-and-resilient-apps

PeppaPig 👍 5

I would go with D. Obviously a single DB instance would become a single point of failure. You can prompt a cross-region read replica to the primary in the case of DR. https://cloud.google.com/sql/docs/mysql/replication/cross-region-replicas

Unfaithful 👍 5

Answer: C Support: Read replicas do not provide failover capability. So option D is out.

kopper2019 👍 2

hey guys new Qs posted as of July 12th, 2021, All 21 new Qs in Question #152

SSV 👍 3

could you please post those question here itself. I am unable to access #152

PeppaPig 👍 9

D is correct. Regional MIG by default ensures resilience of VMs on application layer What you really need to test is the Database layer as there is only a single DB instance that's obviously became single point of failure. Manual failover means you promote a replica as a standalone database, it is a recommended practice by GCP in disaster recovery. Ref: https://cloud.google.com/sql/docs/mysql/replication/cross-region-replicas#promote-a-replica

robotgeek 👍 1

agree, in a MIG shutting down VMs serves no purpose, am I right?

pnearn 👍 1

This is the correct answer + explanation

NYKC 👍 1

C is correct

victory108 👍 4

C. Schedule a disaster simulation exercise during which you can shut off all VMs in a zone to see how your application behaves.

un 👍 1

i would go with C

Ausias18 👍 1

answer is C

lynx256 👍 2

IMO - C is ok. D is about resilience architecture/solution. But we want to TEST their authentication layer for RESILIANCY. A and B are about testing of their authentication layer base functionality, not it's RESILIENCY.

AndreUanKenobi 👍 1

Resilience testing is "Resilience testing is a type of software testing that observes how applications act under stress. It's meant to ensure the product's ability to perform in chaotic conditions without a loss of core functions or data; it ensures a quick recovery after unforeseen, uncontrollable events" I guess it must be C

bnlcnd 👍 1

This is about "resilience testing". only C means something of "resilience testing". B - it sound to me that you just deploy something and wait. Not cover the "test" part.

Arimaverick 👍 3

Answer should be C. Authentication Layer is just an application nothing to do with what is being asked in this question. D is wrong as Cloud SQL should have a failover replica not a read replica for resiliency. Google recommends and its quite logical to have Failover replica in different zone and read replica in same zone. So D is not the option. B is completely incorrect as we are not testing authenticity of the application but the resiliency.

mwilbert 👍 1

C is correct. You aren't testing the authentication itself, you are testing the resilience of the authentication by shutting down a zone and seeing if it still works.

VPK2222 👍 2

Answer is C https://cloud.google.com/solutions/scalable-and-resilient-apps#test_your_resilience

Rothmansua 👍 1

And how is that related to authentication?

ybe_gcp_cert 👍 4

A and B focus on security, intrusion test and scraper scan doesn't test the resiliency which is a broader domain. Which leave C and D. D might do the job but, the problem is changing the configuration by adding a replica. You are supposed to design your application and test it's resilience as is, not add new components. The question doesn't ask about what can you do to improve or implement a DR. it's asking to DO resilience test. I would go with C.

Chulbul_Pandey 👍 1

C is good

SKSKSK 👍 1

I tend to lean towards C: 1) testing authentication layer is just a smoke screen, the key is to test "resilience" of a layer which happened to be authentication layer 2) I also think added read replica is changing infrastructure and not testing existing setup

pepYash 👍 2

This question is quite ambiguous. Resilience talks about the behavior in stress. In this case the authentication layer. None of the options seem to justify the resilient testing. B is the only option that makes a little sense.

N1_arch 👍 1

Answer is C - mention of authentication application in the question is a red-herring. Question is about resiliency testing of a component.

akhadar2001 👍 1

Question is about authentication layer so answer is B.

francisco_guerra 👍 1

Yes but resilence its the same that were talk about any other layer I think its C or D

AshokC 👍 1

C is meaningful

richardxyz 👍 2

C is the answer; D is not correct, a primary instance cannot failover to a read replica and read replicas are unable to failover in any way during an outage.

Ale1973 👍 1

Answer is C for me. Our customer wants to do RESILIENCE testing. A & B are security assessment and D is changing architecture (you are testing another configuration, not your production configuration)

Kabiliravi 👍 1

What is the definition of resiliency tests??? Answer is C. https://cloud.google.com/solutions/scalable-and-resilient-apps

wiqi 👍 3

D is correct, because the ask is about resiliency. Cloud SQL is hosting the authentication DB, hence we have to look at Cloud SQL resiliency. So having a read replica in different zone and triggering the failover will do.

nezih 👍 5

this is about testing resilience not improving. So deploying IDS won't give any idea how resilient our system is. Answer is C

kaush 👍 2

Also C doesnot not mention shutdown all VMs in MIG ,merely shutdown in a zone, hence this really test resiliency hence correct answer is C

motty 👍 3

A is incorrect. It has nothing to do with resilience B is incorrect. it is related to intrusion detection C is incorrect. Usage of MIG will ensure that that load will be swithced to proper zone. D is correct as it is testing component which resilience is not covered by MIG but by CloudSQL funtionality (replica) and this needs to be tested

gfhbox0083 👍 5

C, for sure. When talking about Resilience.

Paul_DSouza 👍 7

The word "resiliency" refers to =============== To test resiliency, you should verify how the end-to-end workload performs under intermittent failure conditions. =============== Under this:- HA - VMs in different zones to prevent app going down when one zone goes down DR - Entire app infra moves to another region with minimum downtime Testing resiliency assumes a degree of HA or DR or both. C is the most proper answer in this case, as it will test resiliency (of everything including authentication) by simulating a downtime (shutting down all VMs in one zone).

Ziegler 👍 3

C is the correct answer The question is assuming that DR setting is already existing and they need to test how the application response if the database (authentication layer fails).

hitmax87 👍 1

It is good approach. Netflix does it. Dont forget that MIG is regional, so probably there will be some machines in the rest AZs.

elaineshi 👍 4

Agree, Chaos testing is to shutdown random instances.

vartiklis 👍 20

You're not testing authentication, you're testing the resilience of the authentication layer. "A resilient app is one that continues to function despite failures of system components" (https://cloud.google.com/architecture/scalable-and-resilient-apps#resilience_designing_to_withstand_failures) - such as shutting down all VMs in a zone.

nrajesh 👍 5

C is the answer. D is misleading. Read replica does not provide failover capability. If it was failover replica, we would have a tie between C and D https://cloud.google.com/sql/docs/mysql/replication/create-replica -"Note: Read replicas do not provide failover capability. To provide failover capability for an instance, see Configuring an Instance for High Availability."

kaush 👍 2

Read Replicas do not provide failover capability Read replicas do not provide failover capability. To provide failover capability for an instance, see Configuring an Instance for High Availability. https://cloud.google.com/sql/docs/mysql/replication/create-replica

AD2AD4 👍 1

Final Decision to go with Option D

AD2AD4 👍 2

Final Decision Updated to go with Option C

gcp_aws 👍 1

I will go with C... The option D also looks good, but it is talking about read replica for cloudsql ,not failover .. and it is not talking about promoting the read replica as primary instance.

Sat_G 👍 4

D - the question says resilience testing of authentication layer. Its using REST API with Cloud SQL ... Cloud SQL could very easily be the layer that does authentication hence having a read replicate and manually trigger a fail over proves the objective. C is an overkill to turn off all your VMs to test authentication resiliency.

amralieg 👍 2

Should be C. A & B are not valid, because they don't want to test the auth itself, but rather its resilience, D is wrong because read replica is not a failover replica

GunjGupta 👍 4

There are 2 key points in Question-- Resiliency testing and authentication layer. The way I read the question, the Authentication layer consists of MIG with Cloud SQL. Hence we need to propose a solution for creating chaos on this (MIG with Cloud SQL). A and B do not seems to reflect resiliency aspects. I will go with C

Jack_in_Large 👍 1

B is right. C is wrong, as the objective is "do resilience testing of their authentication layer" instead of HA or DR testing.

Zarmi 👍 1

Answer: C

toyochik 👍 2

A and B are not tests in the first place. That is Monitoring. D isn't bad but it only tests HA of Cloud SQL without including a regional instance groups. C is better. It deserves resilience testing.

tartar 👍 7

C is ok

SMS 👍 4

Answer is D. Test the resiliency by manually failing over the DB and see if REST API continues to serve.

ronald89 👍 4

D should not be the answer, since "This consists of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance" ; D is creating a read-only instance.

Javed 👍 2

It should be B as it is related to authentication layer.

natpilot 👍 2

I thin C , since the question is asking to do a resilience testing.

MeasService 👍 4

So... again very confusing question. They highlighted first of Authentication layer resilience testing. but.... they continue saying..... THIS CONSIST of regional MIGs and Cloud SQL. When I hear on Resilience testing..... I would look for Is service available when some components down. That leaves me with option C and D. and out of both... C would be one I would go with.

Kri_2525 👍 66

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.

JoseCloudEng1994 👍 1

Note: resilience and high availability are not the same, though they are closely related. High availability is a part of an overall resilience strategy. High availability focuses on keeping a system up and running with minimal downtime. It is primarily concerned with eliminating single points of failure by using redundancy. The goal is to ensure a system is accessible and operational as close to 100% of the time as possible. Key Question: Is the system available? How it's achieved: Through redundant components, load balancing, and automatic failover. If one component fails, a backup is immediately ready to take over.

Jack_in_Large 👍 6

Shutting off all VMs in a zone is not good approach for testing of authentication

kalschi 👍 4

I think the question states the _authentication_layer_ consists of regional MIG and Cloud SQL. so to _resilience_test_ the _authentication_layer_ , it's really to test the MIG and Cloud SQL. So prefer C. Also, intrusion detection software is not TESTING the layer, it's more like a detection and prevention process.

AWS56 👍 1

Agree B

KouShikyou 👍 16

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

Darahaas 👍 4

Resilience testing of the "Authentication Layer", not the "Application". So the answer is B.

Eroc 👍 6

I'm with @jcmoranp and @crypt0 on this one... shutting down the VMs wouldn't test only the authentication layer... same for replication of database (D).. answer B

jcmoranp 👍 2

resilience testing of AUTHENTICATION LAYER, so its A o B. A only tracks for compromised users, B is better because tests with a hacking software. It's B

KouShikyou 👍 5

How about D?

crypt0 👍 4

I am also not sure here, but they say: resilience testing of their _authentication layer_. How does shutting down all vms from one zone test the authentication layer?

MeasService 👍 4

Is it really B? why not C ? It is taking about resilience testing. shutting down all vms from one zone would be ideal testing.

nitinz 👍 1

C is correct. read between lines and eliminate : - Your customer wants to do resilience testing of their authentication layer. This consists of a regional managed instance group serving a public REST API that reads from and writes to a Cloud SQL instance. What should you do? A. Engage with a security company to run web scrapers that look your users' authentication data om malicious websites and notify you if any if found. BULL SHIT B. Deploy intrusion detection software to your virtual machines to detect and log unauthorized access. NOT RELEVANT C. Schedule a disaster simulation exercise during which you can shut off all VMs in a zone to see how your application behaves. NOTHING ELSE TO PICK, SO BE IT D. Configure a read replica for your Cloud SQL instance in a different zone than the master, and then manually trigger a failover while monitoring KPIs for our REST API. READ REPLCA CAN NOT BE WRITTEN TO

joshuaquek 👍 1

Its B, because penetration testing programs test for both resiliency and authentication. Resiliency because it causes a service to go down if it penetrates, infects and takes the service down. Authentication because it tests if it can penetrate the resources, to begin with.

kumarp6 👍 2

C it is

SMS 👍 8

Ignore above. Answer is C

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Expert Analysis

Why the Answer Is Correct

Option C is correct because resilience testing specifically evaluates whether a system continues to function despite failures of its components. Shutting off all VMs in a zone simulates a realistic failure scenario and tests whether the regional managed instance group can automatically redistribute traffic to healthy zones. This aligns directly with Google Cloud's guidance on resilience: a resilient application should withstand the loss of one or more compute resources. By monitoring application behavior during this simulated failure, you gain actionable insight into the authentication layer's actual resilience posture.

Why the Other Options Are Wrong

Option A describes credential monitoring services (like Google's Dark Web monitoring), which is a security measure, not resilience testing—it does not test how the system behaves under failure conditions. Option B deploys intrusion detection software, which addresses unauthorized access detection, a security concern rather than a resilience or availability concern. Option D proposes configuring a Cloud SQL read replica and manually triggering failover; however, Google's documentation explicitly states that read replicas do not provide failover capability. Additionally, the REST API performs writes, which a read replica cannot serve, making this approach technically unsound for the described workload.

Community Comment Notes

Multiple commenters converge on C, with vartiklis clarifying the distinction between testing authentication itself versus testing "the resilience of the authentication layer" by simulating component failure. PeppaPig initially argues for D, reasoning that the database is the single point of failure, but Tamim321 correctly counters that "Read replicas do not provide failover capability" per Google's own documentation. juliansierra further notes that because the REST API reads and writes, a read replica alone cannot handle writes, reinforcing that D is technically flawed. Kri_2525 anchors the answer in Google's scalable and resilient apps documentation, where resilience is defined as the ability to withstand unexpected failures.

Official Reference

Exam Strategy

When you see 'resilience testing' or 'disaster simulation' in the question stem, focus on options that directly simulate component failure (e.g., shutting down VMs in a zone) rather than monitoring or detective controls. Also verify vendor-specific limitations—Google Cloud read replicas explicitly do not provide failover capability, which eliminates database-failover distractors.

Frequently Asked Questions

Why can't I use a Cloud SQL read replica to test failover for the authentication layer?

Google Cloud documentation states that read replicas do not provide failover capability; they are for read scaling. For HA failover, you need a regional HA configuration with a standby instance in another zone.

Is shutting down VMs in a zone considered proper resilience testing?

Yes. Simulating a zone failure directly tests whether the regional MIG can withstand the loss of compute resources in one zone, which is a core principle of resilience design.

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