Maximum Number of Shards with Cluster Mode Enabled

Answer: B.

A deployment of Amazon ElastiCache for Redis with cluster mode enabled can have a maximum of 90 nodes.

Each shard can consist of one primary node and up to five read replica nodes.

Thus, with five read replicas, each shard consists of six nodes in total.

This means that with five read replicas per shard, the maximum number of shards is 15

Therefore, Option B is CORRECT, and other options are incorrect.

Reference:

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Replication.html https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/Replication.Redis-RedisCluster.html

With Amazon ElastiCache for Redis cluster mode enabled, each shard can have up to 5 read replicas. Therefore, the maximum number of shards that can be deployed depends on the maximum number of read replicas that can be created in a single ElastiCache cluster.

According to the AWS documentation, the maximum number of read replicas for a single Redis cluster in ElastiCache is 5. This means that the maximum number of shards that can be deployed is 15 (since 5 read replicas per shard is allowed).

To understand this calculation, consider the following:

• Each shard in ElastiCache for Redis with cluster mode enabled can have up to 5 read replicas.
• A Redis cluster in ElastiCache can have up to 3 shards.

Therefore, the maximum number of read replicas that can be deployed in a single ElastiCache cluster is:

5 read replicas per shard x 3 shards per cluster = 15 read replicas per cluster

This means that the maximum number of shards that can be deployed in a single ElastiCache cluster is:

15 read replicas per cluster / 5 read replicas per shard = 3 shards per cluster

Therefore, the correct answer to the question is B. 15.