# High-Cardinality Custom Metrics in CloudWatch Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/high-cardinality-custom-metrics-in-cloudwatch A classic CloudWatch metric is identified by its namespace, name and dimensions, and CloudWatch treats every unique combination of dimension values as... By: PointFive Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) The short version A classic CloudWatch metric is identified by its namespace, name and dimensions, and CloudWatch treats every unique combination of dimension values as a separate metric. PointFive Research Cloud cost research at PointFive AWS service [AWS CloudWatch](https://www.pointfive.co/efficiency-hub/cloud-services/aws-cloudwatch) Category [Other](https://www.pointfive.co/efficiency-hub/service-category/other) Reference CER-0379 Type Excessive Ingestion or Processing ## Explanation Why the waste happens and who it affects. Each of those is billed as a custom metric for every hour it receives data. When applications or agents attach dimensions with many possible values, such as request ID, user or customer ID, session ID, pod or container name, IP address or full URL path, one logical metric like Latency turns into thousands or millions of billable metrics. The problem is easy to create by accident with the embedded metric format, where AWS warns that metrics based on high-cardinality dimensions such as requestId create a custom metric for each unique combination, and with PutMetricData or agent configurations that append per-instance or per-container dimensions. It is common in microservice and container environments, where short-lived tasks and pods keep generating new dimension values, and it shows up as custom metric charges growing faster than the workload. ## Billing model The pricing dimensions that drive this cost. Classic custom metrics, including those created from embedded metric format logs, are billed per metric per month. Custom metric Billed per metric-month in volume tiers ($0.30 for the first 10,000, $0.10 for the next 240,000, $0.05 above 250,000 in AWS pricing examples) Hourly proration Metrics are prorated by the hour and charged only in hours when data is sent, so short-lived dimension values still add cost Dimension combination Every unique combination of dimension values is a separate billable metric, even with the same metric name EMF log charges Embedded metric format also incurs log ingestion and archival charges for the log events that carry the metrics ## How to detect 4 checks to find it in your estate. - In Cost Explorer or the Cost and Usage Report, filter CloudWatch usage type MetricMonitorUsage and break it down by operation (MetricStorage for PutMetricData, MetricStorage:AWS/Logs-EMF for embedded metrics) to see which source drives metric count - Use list-metrics per custom namespace and count distinct values for each dimension name to find dimensions with unbounded values - Review EMF payloads, client library code and CloudWatch agent configurations for dimensions built from identifiers such as request, user, session, container or pod IDs - Track the total custom metric count per namespace over time and flag namespaces whose count grows with traffic or deployments rather than with the number of services ## How to fix 5 ways to remove the waste. - Remove unbounded identifiers from dimensions and keep them as log properties instead, so they remain queryable in CloudWatch Logs Insights without creating metrics - Aggregate before publishing, for example per service, operation or status code instead of per request, per user or per container - Limit the dimension sets declared in EMF metric directives and in agent configurations to the combinations actually used in dashboards and alarms - Where per-entity metrics are genuinely needed, evaluate publishing them as OpenTelemetry metrics, which CloudWatch bills per GB ingested ($0.50 per GB on the pricing page) with no charge for the number of unique metric series, instead of as classic custom metrics - Review the change with dashboard and alarm owners first, because alarms and graphs that reference removed dimension combinations will stop receiving data ## Documentation Vendor references for pricing and configuration. - [Amazon CloudWatch Pricing aws.amazon.com](https://aws.amazon.com/cloudwatch/pricing/) - [Analyzing, optimizing, and reducing CloudWatch costs docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch_billing.html) - [Metrics concepts - Amazon CloudWatch docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch_concepts.html) - [Embedding metrics within logs docs.aws.amazon.com](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format.html) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - AWS CloudWatch CER-0233 ### [Overly Permissive VPC Flow Log Filters Sent to CloudWatch Logs](https://www.pointfive.co/efficiency-hub/inefficiencies/overly-permissive-vpc-flow-log-filters-sent-to-cloudwatch-logs) VPC Flow Logs configured with the ALL filter and delivered to CloudWatch Logs often result in unnecessarily high log ingestion volumes - especially in high-traffic environments. This setup is rarely required for day-to-day monitoring or... Other - AWS CloudWatch CER-0380 ### [Excessive CloudWatch GetMetricData API Polling by Monitoring Tools](https://www.pointfive.co/efficiency-hub/inefficiencies/excessive-cloudwatch-getmetricdata-api-polling-by-monitoring-tools) Third-party observability platforms, open source exporters and in-house scripts usually collect AWS metrics by calling the CloudWatch GetMetricData API on a schedule. GetMetricData is billed by the number of metrics requested and, unlike... Other - AWS CloudWatch CER-0224 ### [Suboptimal Log Class Configuration in CloudWatch](https://www.pointfive.co/efficiency-hub/inefficiencies/suboptimal-log-class-configuration-in-cloudwatch) By default, CloudWatch Log Groups use the Standard log class, which has a higher per-GB ingestion price. AWS also offers an Infrequent Access (IA) log class designed for logs that are rarely queried - such as audit trails, debugging... Other --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.