AWS EFS throughput modes: Bursting, Elastic, and Provisioned cost

Quick answer

EFS bills storage (Standard or Infrequent Access) plus a throughput component that depends on mode: Bursting scales throughput with storage size at no extra charge, Elastic bills per throughput actually used (ideal for spiky, unpredictable workloads), and Provisioned bills for a throughput level you set regardless of use. Match the mode to your throughput pattern to avoid over-paying or throttling.

Amazon EFS is elastic NFS, and beyond storage it charges for throughput in one of three modes. The mode is a cost-and-performance decision: pick wrong and you either pay for throughput you do not use or get throttled when you need it. Storage class (Standard or Infrequent Access) is a separate lever.

The three throughput modes

Mode	Throughput cost	Best for
Bursting	None extra; scales with storage size	Throughput proportional to data size
Elastic	Per throughput actually used	Spiky, unpredictable workloads
Provisioned	Per provisioned throughput level	High, steady throughput on small data

Bursting mode gives throughput proportional to how much you store, with no separate throughput charge, and burst credits for spikes. It works when your throughput needs scale with data size. A small file system with high throughput needs will throttle in Bursting.

Elastic and Provisioned

Elastic throughput bills only for the throughput you actually use, scaling automatically, which suits spiky and unpredictable workloads where you cannot predict throughput and do not want to provision. Provisioned throughput lets you set a fixed throughput level, billed whether or not you use it, which suits high, steady throughput against a small amount of data (where Bursting would throttle). Provisioning more than you use is the common overspend.

Storage classes matter too

On top of throughput mode, EFS has Standard and Infrequent Access storage classes, with lifecycle policies moving cold files to the cheaper IA class automatically. This is the storage equivalent of choosing between EFS, EBS, and S3, applied within EFS.

Choosing the mode

Use Bursting when throughput scales with data size, Elastic for spiky unpredictable workloads (pay only for what you use), and Provisioned only for high steady throughput on small data, sized to real need. Combine with IA lifecycle policies for cold data. The wrong mode either throttles performance or pays for idle throughput, so match it to your access pattern.

FAQ

What are the EFS throughput modes and how do they price?

Bursting scales throughput with storage size at no extra charge, Elastic bills per throughput actually used, and Provisioned bills for a throughput level you set regardless of use. All modes also pay for storage in the Standard or Infrequent Access class. The mode should match your throughput pattern.

When should I use EFS Elastic throughput?

For spiky, unpredictable workloads where you cannot forecast throughput. Elastic scales automatically and bills only for the throughput you actually use, so you avoid both throttling and paying for provisioned throughput that sits idle. It suits variable access patterns well.

When should I use EFS Provisioned throughput?

For workloads that need high, steady throughput against a relatively small amount of data, where Bursting mode (which scales throughput with size) would throttle. Provisioned lets you set a fixed throughput level, but you pay for it whether used or not, so size it to real need.

Is EFS Bursting mode free?

The throughput itself carries no separate charge in Bursting mode; you pay only for storage. Throughput scales with how much you store, plus burst credits for spikes. It works when throughput needs are proportional to data size, but a small file system with high throughput needs will throttle.

How do I reduce EFS cost?

Match the throughput mode to your access pattern (Bursting when throughput scales with size, Elastic for spiky, Provisioned only for high steady throughput on small data), use Infrequent Access with lifecycle policies for cold files, and avoid provisioning more throughput than you use.

Does C3X estimate EFS cost?

C3X prices the aws_efs_file_system resource and its configuration from your Terraform, including throughput mode and provisioned throughput where set. Storage volume and actual throughput used depend on usage, which you provide as assumptions.

What to do next

Right-size your file storage before you deploy. C3X reads your Terraform and prices EFS and the rest of your stack against a live catalog. Start with the quickstart.