Exam AWS Certified Database - Specialty topic 1 question 44 discussion

cannot enable Cluster Mode on an existing cluster, With cluster mode disabled it will allow only vertical scaling.

Elasticache now supports enabling cluster mode on existing clusters. https://aws.amazon.com/about-aws/whats-new/2023/05/amazon-elasticache-redis-cluster-mode-configuration-existing-clusters/#:~:text=Amazon%20ElastiCache%20for%20Redis%20now%20supports%20enabling%20Cluster%20Mode%20configuration%20on%20existing%20clusters,-Posted%20On%3A%20May&text=You%20can%20now%20update%20your,data%2C%20or%20affect%20application%20availability.

Elasticache now supports enabling cluster mode on existing clusters. https://aws.amazon.com/about-aws/whats-new/2023/05/amazon-elasticache-redis-cluster-mode-configuration-existing-clusters/#:~:text=Amazon%20ElastiCache%20for%20Redis%20now%20supports%20enabling%20Cluster%20Mode%20configuration%20on%20existing%20clusters,-Posted%20On%3A%20May&text=You%20can%20now%20update%20your,data%2C%20or%20affect%20application%20availability.

B. Increase the size of the ElastiCache cluster nodes to a larger instance size. https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Scaling.RedisReplGrps.html

C is correct

Option B (increasing the size of cluster nodes) can provide some level of scaling, but it may have limitations in terms of the maximum capacity it can handle. Additionally, simply increasing the node size may not fully address the anticipated higher write load during the gaming event. Option C: Creating an additional ElastiCache cluster and load-balancing traffic between the clusters allows for distributing the write load across multiple clusters, effectively scaling the capacity and handling increased demand. This approach provides horizontal scalability and helps mitigate the potential performance limitations of a single cluster. Why not C?

B Redis (cluster mode disabled) supports scaling. You can scale read capacity by adding or deleting replica nodes, or you can scale capacity by scaling up to a larger node type.

Answer:B

B is correct. You cannot enable Cluster Mode on an existing cluster

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Replication.Redis-RedisCluster.html Reads v. writes – If the primary load on your cluster is applications reading data, you can scale a Redis (cluster mode disabled) cluster by adding and deleting read replicas. However, there is a maximum of 5 read replicas. If the load on your cluster is write-heavy, you can benefit from the additional write endpoints of a Redis (cluster mode enabled) cluster with multiple shards.

I think answer is B. With cluster mode disabled it will allow only vertical scaling. So going with B

A is the correct answer Enabling Cluster Mode provides a number of additional benefits in scaling your cluster. In short, it allows you to scale in or out the number of shards (horizontal scaling) versus scaling up or down the node type (vertical scaling). This means that Cluster Mode can scale to very large amounts of storage (potentially 100s of terabytes) across up to 90 shards, whereas a single node can only store as much data in memory as the instance type has capacity for. https://aws.amazon.com/blogs/database/work-with-cluster-mode-on-amazon-elasticache-for-redis/