An IT firm has implemented caching for its three-tier application using multi-node Memcached clusters as a front-end to Amazon DynamoDB. The ElastiCache Memcached PHP client is used which is configured in auto-discovery mode. Recently the operations team has performed the addition of nodes in this cluster. After adding a node to a multi-node Memcached cluster, many cache misses are observed that are overloading the database.
What can be configured to avoid this issue?

Answer options:

A.Use consistent hashing.
B.While adding nodes, use --apply-immediately parameter.
C.Use Write-through caching.
D.Change the endpoints in the application for new nodes.

Correct Answer: A
Cache Keys need to be spread across all nodes in an Amazon ElastiCache for better caching performance. In a normal scenario, when a new node is added to a cluster, many keys need to be moved, resulting in a cache miss. To avoid this, consistent hashing can be used to have better caching performance whenever new nodes are added to a cluster. 
Option B is incorrect as this parameter will add nodes immediately to the cluster. This will not have an impact on cache misses.
Option C is incorrect as Write-through is one of the caching strategies which will write data in cache whenever data is written in the database. This will not impact cache misses when a new node is added to the multi-node cluster.
Option D is incorrect as Since auto-discovery is enabled, changing endpoints in the application is not required.
For more information on Amazon ElastiCache, refer to the following URL,
https://docs.aws.amazon.com/AmazonElastiCache/latest/mem-ug/BestPractices.LoadBalancing.html