AWS Neptune cost: provisioned instances vs Serverless, plus I/O

Quick answer

Neptune bills per instance hour when provisioned or per Neptune Capacity Unit (NCU) hour when Serverless, plus $0.10 per GB-month storage and $0.20 per million I/O. Serverless suits spiky or unpredictable graph workloads; provisioned is cheaper for steady load. As with any Aurora-style engine, I/O scales with query patterns.

Neptune is a graph database with the Aurora billing shape: compute, storage, and I/O. The first decision is provisioned instances versus Serverless, and it is the same steady-versus-spiky tradeoff you make everywhere else in AWS.

Provisioned vs Serverless

Provisioned instances cost a fixed hourly rate per node regardless of load, which is cheapest when your graph traffic is steady and predictable. Neptune Serverless bills per NCU-hour and scales capacity up and down with demand, which wins when load is spiky, unpredictable, or often idle, since you stop paying for a large idle instance. The crossover is the same logic as other serverless-versus-provisioned database choices: steady load favors provisioned, variable load favors serverless.

Storage and I/O

Dimension	Rate (approximate)
Provisioned instance	Per node hour, by class
Serverless	Per NCU-hour
Storage	~$0.10 / GB-month
I/O	~$0.20 / million requests

I/O follows your traversals

Graph queries that traverse many hops or scan large portions of the graph generate more I/O. Well-modeled graphs and selective queries keep I/O down, while unbounded traversals drive it up. Review expensive traversals before assuming you need a bigger instance.

Controlling the bill

Pick Serverless for intermittent or bursty workloads and set a sensible maximum NCU so a runaway query cannot scale cost without bound. For steady production load, size a provisioned instance to peak and add read replicas only for scaling or availability. Stop non-production clusters off-hours, the same habit as the reduce-your-cloud-bill checklist.

FAQ

How is Neptune priced?

Per instance hour when provisioned or per Neptune Capacity Unit (NCU) hour when Serverless, plus storage at about $0.10 per GB-month and I/O at about $0.20 per million requests. Storage and I/O follow the Aurora billing model.

Is Neptune Serverless cheaper than provisioned?

For spiky, unpredictable, or often-idle workloads, yes, because it scales capacity to demand and you stop paying for a large idle instance. For steady, predictable load a provisioned instance is usually cheaper. Match the mode to your traffic shape.

What drives Neptune I/O cost?

Query traversals. Queries that walk many hops or scan large portions of the graph generate more I/O, while selective queries on a well-modeled graph keep it low. Review expensive traversals before scaling up compute.

How do I cap Neptune Serverless cost?

Set a maximum NCU limit so a runaway or expensive query cannot scale capacity, and therefore cost, without bound. Combine that ceiling with query review so the workload stays within a predictable range.

How do I reduce Neptune cost overall?

Choose the right mode for your traffic, size provisioned instances to peak, add replicas only when needed, cap Serverless NCU, and stop non-production clusters off-hours. Optimize expensive traversals rather than adding compute.

Does C3X estimate Neptune cost?

C3X prices aws_neptune_cluster and its instances from your Terraform so compute and storage appear before deploy. I/O and Serverless scaling depend on query load, which you provide as a usage assumption.

What to do next

Price your graph database before deploy. C3X reads your Terraform and prices Neptune and the rest of your stack against a live catalog. Try the quickstart.