aws_neptune_cluster_instance cost estimation
A compute instance in a Neptune graph-database cluster, billed per instance-hour by class. A db.r5.large runs ~$254/month, and a cluster usually has a writer plus readers.
An aws_neptune_cluster_instance is a compute node in an Amazon Neptune graph database cluster (the cluster, aws_neptune_cluster, holds the shared storage). Each instance bills per instance-hour by class, continuously — a db.r5.large is ~$0.348/hour, about $254/month.
Like Aurora, the total compute bill is the sum of the cluster's instances: a writer plus any readers. A production cluster with a writer and one reader on db.r5.large is ~$508/month before storage and I/O (which bill on the cluster). Each reader is a full-price instance that adds read throughput and a failover target.
The cost levers are the instance class (right-size to graph query load) and the reader count (match to read throughput and HA needs). Reserved instances discount steady cluster nodes.
c3x prices the instance from instance_class; sum across the cluster's instances for total compute, with storage and I/O on the aws_neptune_cluster.
Terraform example
A minimal but realistic configuration that C3X can estimate.
resource "aws_neptune_cluster_instance" "writer" {
cluster_identifier = aws_neptune_cluster.main.id
instance_class = "db.r5.large"
}
resource "aws_neptune_cluster_instance" "reader" {
cluster_identifier = aws_neptune_cluster.main.id
instance_class = "db.r5.large"
}Pricing dimensions
What you actually pay for when you provision aws_neptune_cluster_instance.
| Dimension | Unit | What's being charged |
|---|---|---|
| Neptune instance | per hour | Per instance-hour by class, billed continuously. Each writer and reader is a separate instance. $0.348/hour ≈ $254.04/month for db.r5.large |
| Storage & I/O | per GB-month / per request | Neptune storage and I/O bill on the cluster (aws_neptune_cluster), not the instance. |
Sample C3X output
One db.r5.large Neptune instance, 24/7 (a cluster usually has 2+):
aws_neptune_cluster_instance.writer
└─ Neptune instance (db.r5.large) 730 hours $254.04
Monthly $254.04Optimization tips
Common ways to reduce aws_neptune_cluster_instance cost without changing the workload.
Right-size the instance class
Difference between classesNeptune instance cost scales with class. Monitor CPU and memory against graph query load and step down classes that are over-provisioned. A db.t3.medium (~$0.084/hour) suits dev and light workloads.
Match reader count to need
~$254/month per removed db.r5.large readerEach reader is a full-price instance. One reader gives a failover target and read scaling; add more only for genuine read throughput needs.
Reserve steady cluster instances
Up to ~50% on steady instancesReserved instances discount the always-on writer and readers for a 1-3 year commitment — the biggest lever for a production graph database.
Use Neptune Serverless for variable load
Workload-dependentNeptune Serverless scales capacity (NCUs) to demand instead of running fixed instances 24/7, which can be cheaper for spiky or intermittent graph workloads.
FAQ
How is a Neptune cluster instance billed?
Per instance-hour by class, continuously — a db.r5.large is ~$254/month. Storage and I/O bill separately on the cluster (aws_neptune_cluster). Total compute is the sum of the cluster's writer and reader instances.
Does each Neptune reader cost extra?
Yes — every reader is a full-price instance at its class rate. Readers add read throughput and failover targets, so size the count to your real read load and availability target.
How does c3x estimate the cost?
From instance_class, pricing the per-instance hour. Sum across the cluster's aws_neptune_cluster_instance resources for total compute; storage and I/O are priced on the aws_neptune_cluster.
Should I use Neptune Serverless instead?
For variable or intermittent graph workloads, Serverless scales capacity to demand and can be cheaper than fixed instances running 24/7. Steady high load stays cheaper on provisioned instances.
Related resources
Estimate this resource in your own Terraform
Free, open source, no API key. C3X parses your Terraform and shows line-item cost for every resource, including aws_neptune_cluster_instance.