What is the MOST likely reason for this occurrence?
A VPC endpoint was not added to access DynamoDB.
Strongly consistent reads are always passed through DAX to DynamoDB.
DynamoDB is scaling due to a burst in traffic, resulting in degraded performance.
A VPC endpoint was not added to access CloudWatch.
Explanations:
A VPC endpoint is not required to access DynamoDB. DynamoDB can be accessed without a VPC endpoint if it is configured with an internet gateway or Direct Connect.
Strongly consistent reads bypass the DAX cache and are directly fetched from DynamoDB. This would cause QueryCacheMisses to increase and QueryCacheHits to stay at 0.
DynamoDB scaling due to burst traffic does not explain the continuous increase in QueryCacheMisses. The issue is related to the read consistency, not traffic load.
A VPC endpoint for CloudWatch is unnecessary to access CloudWatch metrics. This option is unrelated to the DAX query cache behavior.
I map out that the answer is:
Strongly consistent reads are always passed through DAX to DynamoDB.
In my opinion, the answer is:
Strongly consistent reads are always passed through DAX to DynamoDB.