How to implement AWS RDS Read/Write Latency Cloudwatch alarms using Terraform

Question

I want to set new AWS RDS Read/Write Latency Cloudwatch alarms using Terraform. I have googled a alot to find some examples for the same but i didn't find any.

what i have wrote in the terraform main.tf. Is this code snippet correct or not?

resource "aws_cloudwatch_metric_alarm" "postgres_write_latency" {
  count               = length(var.db_instance_identifier)
  alarm_name          = "rds-postgres-write-latency-canada"
  comparison_operator = "GreaterThanOrEqualToThreshold"
  evaluation_periods  = "1"
  metric_name         = "WriteLatency"
  namespace           = "AWS/RDS"
  period              = "60"
  statistic           = "Average"
  threshold           = "2"
  treat_missing_data  = "breaching"

  dimensions = {
    DBInstanceIdentifier    = element(var.db_instance_identifier, count.index)
  }

  alarm_description = "Write IOPS for rds postgres in Canada ${terraform.workspace}"
  alarm_actions     = [var.sns_topic] 
  ok_actions        = [var.sns_topic]
}

resource "aws_cloudwatch_metric_alarm" "postgres_read_latency" {
  count               = length(var.db_instance_identifier)
  alarm_name          = "rds-postgres-read-latency-canada"
  comparison_operator = "GreaterThanOrEqualToThreshold"
  evaluation_periods  = "1"
  metric_name         = "ReadLatency"
  namespace           = "AWS/RDS"
  period              = "60"
  statistic           = "Average"
  threshold           = "0.030"
  treat_missing_data  = "breaching"

  dimensions = {
    DBInstanceIdentifier    = element(var.db_instance_identifier, count.index)
  }

  alarm_description = "Read IOPS for rds postgres in Canada ${terraform.workspace}"
  alarm_actions     = [var.sns_topic] 
  ok_actions        = [var.sns_topic]
}

I have implemented this code but it start spamming the slack channel due to INSUFFICIENT_DATA.

I need a working terraform code for AWS RDS Read/Write Latency Cloudwatch alarms.