A user has configured an ELB to distribute the traffic among multiple instances. The user instances are facing some
issues due to the back-end servers. Which of the below mentioned CloudWatch metrics helps the user understand the
issue with the instances?

A.
HTTPCode_Backend_3XX

B.
HTTPCode_Backend_4XX

C.
HTTPCode_Backend_2XX

D.
HTTPCode_Backend_5XX

Explanation:
CloudWatch is used to monitor AWS as well as the custom services. For ELB, CloudWatch provides various metrics
including error code by ELB as well as by back-end servers (instances). It gives data for the count of the number of HTTP
response codes generated by the back-end instances. This metric does not include any response codes generated by
the load balancer. These metrics are:
– The 2XX class status codes represents successful actions
– The 3XX class status code indicates that the user agent requires action

– The 4XX class status code represents client errors
– The 5XX class status code represents back-end server errors