CloudBurn Rules

ElastiCache Rules

CloudBurn cost optimization rules for AWS ElastiCache.

These rules flag ElastiCache clusters that are idle or running on-demand when reserved node pricing would save you money.

Rule IDScan TypeName
CLDBRN-AWS-ELASTICACHE-1DiscoveryElastiCache Cluster Missing Reserved Coverage
CLDBRN-AWS-ELASTICACHE-2DiscoveryElastiCache Cluster Idle

CLDBRN-AWS-ELASTICACHE-1

ElastiCache Cluster Missing Reserved Coverage

Scan type: Discovery

What it checks

Flags ElastiCache clusters that have been running for at least 180 days without matching active reserved node coverage. The rule normalizes node sizes into capacity units and checks whether your reserved inventory covers each cluster's actual footprint.

Valkey clusters can consume reserved coverage from Valkey, Redis, or wildcard engine buckets. Node types with unknown sizes fall back to exact-type matching.

Why it matters

ElastiCache Reserved Nodes offer up to 55% savings over on-demand pricing for 1-year terms and even more for 3-year commitments. A cluster that has been running for 6+ months without reserved coverage is almost certainly a candidate for a reservation. The longer a cluster runs on-demand, the more money you leave on the table.

What triggers a finding

All of the following must be true:

  • Cluster status is available
  • Cluster has been running for 180 or more days
  • The cluster's normalized capacity exceeds the remaining reserved node coverage for its region:nodeType:engine combination

How to remediate

  1. Review the flagged cluster's node type, engine, and node count
  2. Check your current reserved node inventory for gaps in coverage
  3. Purchase a reserved node that matches the cluster's configuration:
aws elasticache purchase-reserved-cache-nodes-offering \
  --reserved-cache-nodes-offering-id <offering-id> \
  --cache-node-count 1

Consider using the AWS Cost Explorer Reserved Instance recommendations to identify the most cost-effective reservation terms for your usage patterns.

CLDBRN-AWS-ELASTICACHE-2

ElastiCache Cluster Idle

Scan type: Discovery

What it checks

Flags available ElastiCache clusters whose 14-day average cache hit rate stays below 5% and average current connections stay below 2.

Why it matters

An ElastiCache cluster with negligible cache hits and almost no connections is not providing caching value. ElastiCache nodes are billed per hour regardless of utilization. A cache.r6g.large cluster costs roughly $200/month. If it's not being used, that's pure waste.

What triggers a finding

cacheClusterStatus is available AND averageCacheHitRateLast14Days is less than 5 AND averageCurrentConnectionsLast14Days is less than 2 (both non-null).

How to remediate

Verify that the application is configured to use the cluster. If the cluster is genuinely unused, delete it. If it's supposed to be used, investigate why the application isn't connecting (wrong endpoint, DNS mismatch, security group blocking).

aws elasticache delete-cache-cluster --cache-cluster-id my-cluster-id

See Also

← EKSELB →