Exam AWS-SysOps topic 1 question 788 discussion

A. Scale the cluster by adding additional nodes Also, if you are experiencing evictions with your cluster, it is usually a sign that you need to scale up (use a node that has a larger memory footprint) or scale out (add additional nodes to the cluster) in order to accommodate the additional data. An exception to this rule is if you are purposefully relying on the cache engine to manage your keys by means of eviction, also referred to an LRU cache. https://aws.amazon.com/caching/implementation-considerations/

Found this interesting read on Evictions:- "Evictions happen when the cache memory usage limit (maxmemory for Redis) is reached and the cache engine has to remove items to make space for new writes. Unlike the host memory, which leads to swap usage when exceeded, the cache memory limit is defined by your node type and number of nodes. The evictions follow the method defined in your cache configuration, such as LRU for Redis. Evicting a large number of keys can decrease your hit rate, leading to longer latency times. If your eviction rate is steady and your cache hit rate isn’t abnormal, then your cache has probably enough memory. If the number of evictions is growing, you should increase your cache size by migrating to a larger node type (or adding more nodes if you use Memcached)."

When the eviction count is high, it means that the cache size is not sufficient to hold all the frequently used data. Adding additional nodes to the ElastiCache Memcached cluster will increase the overall cache size and allow more data to be stored, reducing the eviction rate and improving cache hit rates.

A is the answer

A is the answer Scale the cluster by adding more nodes

Will go with A

A. Scale the cluster by adding additional nodes : Seems correct

I'll go with A

A. Scale the cluster by adding additional nodes

A is correct ... read replica nodes only apply for Amazon ElastiCache for Redis