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Exam AWS Certified Solutions Architect - Professional topic 1 question 13 discussion

Exam question from Amazon's AWS Certified Solutions Architect - Professional
Question #: 13
Topic #: 1
[All AWS Certified Solutions Architect - Professional Questions]

Your application is using an ELB in front of an Auto Scaling group of web/application servers deployed across two AZs and a Multi-AZ RDS Instance for data persistence.
The database CPU is often above 80% usage and 90% of I/O operations on the database are reads. To improve performance you recently added a single-node
Memcached ElastiCache Cluster to cache frequent DB query results. In the next weeks the overall workload is expected to grow by 30%.
Do you need to change anything in the architecture to maintain the high availability or the application with the anticipated additional load? Why?

  • A. Yes, you should deploy two Memcached ElastiCache Clusters in different AZs because the RDS instance will not be able to handle the load if the cache node fails.
  • B. No, if the cache node fails you can always get the same data from the DB without having any availability impact.
  • C. No, if the cache node fails the automated ElastiCache node recovery feature will prevent any availability impact.
  • D. Yes, you should deploy the Memcached ElastiCache Cluster with two nodes in the same AZ as the RDS DB master instance to handle the load if one cache node fails.
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Suggested Answer: A 🗳️
by ExtHo at March 16, 2021, 7:14 p.m.
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amministrazione
8 months, 3 weeks ago
A. Yes, you should deploy two Memcached ElastiCache Clusters in different AZs because the RDS instance will not be able to handle the load if the cache node fails.
upvoted 1 times
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AimarLeo
1 year, 3 months ago
Selected Answer: A
A seems the one
upvoted 1 times
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ramyboudakka
1 year, 7 months ago
Selected Answer: A
D is wrong because "2 nodes in the same AZ"
upvoted 1 times
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yd_h
1 year, 7 months ago
Selected Answer: A
https://docs.aws.amazon.com/AmazonElastiCache/latest/mem-ug/FaultTolerance.html "To mitigate the impact of a node failure, spread your cached data over more nodes. Because Memcached does not support replication, a node failure will always result in some data loss from your cluster." This means a node failure would result in 50% of data loss. RDS I/O and CPU usage are on the edges and expected that the workload will be increased by 30%.
upvoted 1 times
yd_h
1 year, 7 months ago
50% of data loss approximately in this case
upvoted 1 times
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SkyZeroZx
1 year, 11 months ago
Selected Answer: A
The correct answer is A. Yes, you should deploy two Memcached ElastiCache Clusters in different AZs because the RDS instance will not be able to handle the load if the cache node fails. The current architecture has a single-node Memcached ElastiCache Cluster. If this node fails, the application will not be able to cache any frequently accessed data from the database. This will cause the database to experience increased load, as it will have to handle all of the read requests directly. If the database is unable to handle this increased load, it may become unavailable. By deploying two Memcached ElastiCache Clusters in different AZs, the application can continue to cache frequently accessed data even if one of the clusters fails. This will help to reduce the load on the database and prevent it from becoming unavailable.
upvoted 2 times
SkyZeroZx
1 year, 11 months ago
Option B: No, if the cache node fails you can always get the same data from the DB without having any availability impact. This is not entirely true. If the cache node fails, the application will have to fetch the data from the database directly. This may cause a temporary increase in latency for the application. Option C: No, if the cache node fails the automated ElastiCache node recovery feature will prevent any availability impact. This is true, but it is not a reliable solution. The automated node recovery feature can take several minutes to restore a failed node. This could lead to a significant availability impact for the application.
upvoted 2 times
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SkyZeroZx
1 year, 11 months ago
Option D: Yes, you should deploy the Memcached ElastiCache Cluster with two nodes in the same AZ as the RDS DB master instance to handle the load if one cache node fails. This is not a good solution. If the AZ where the RDS DB master instance is located becomes unavailable, the application will not be able to access any data from the database. In summary, the best way to maintain high availability for the application is to deploy two Memcached ElastiCache Clusters in different AZs. This will ensure that the application can continue to cache frequently accessed data even if one of the clusters fails.
upvoted 2 times
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eth1
2 years, 1 month ago
Selected Answer: D
why 2 cluster, just add more node in the current cluster
upvoted 3 times
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TechX
2 years, 10 months ago
Selected Answer: A
It's A
upvoted 1 times
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tkanmani76
3 years, 3 months ago
While A works, it involves additional cost. Whereas Elasticache supports node recovery on failure. Believe that would be good enough to take care, there may be momentary impact during that time alone.
upvoted 2 times
tkanmani76
3 years, 3 months ago
Hence C look right.
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Akhil254
3 years, 6 months ago
A Correct
upvoted 1 times
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01037
3 years, 7 months ago
A for sure
upvoted 1 times
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ExtHo
3 years, 7 months ago
yes A is correct
upvoted 1 times
nitinz
3 years, 7 months ago
great explanation, a is correct.
upvoted 1 times
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