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Most teams buying an AWS Compute Savings Plan are thinking about EC2. They know it covers EC2. What they are less clear on is how it applies to Fargate and Lambda — and the partial coverage of both services is exactly where budget assumptions go wrong.
The Compute Savings Plan does cover Fargate. It does cover Lambda. But not all charges on either service. Fargate’s OS license fees and ephemeral storage are excluded. Lambda’s request charges are excluded entirely. If you have a Lambda-heavy architecture and assume you are getting 66% off your entire Lambda bill, you are not — you are getting 17% off the duration component only. The math is very different.
This guide covers exactly which charges are discounted, which are not, and how to read your bill to see whether the coverage is working the way you expect.
Also read: The Complete Guide to Compute Savings Plans (AWS and Azure)
The Complete Service Eligibility Table
| Charge Type | Service | Covered? | Max Discount | Notes |
| vCPU hours | Fargate (ECS/EKS) | YES — Covered | Up to ~52% (3-yr) | Linux/x86 on-demand: $0.04048/hr |
| Memory (GB/hr) | Fargate (ECS/EKS) | YES — Covered | Up to ~52% (3-yr) | Linux/x86 on-demand: $0.004445/GB-hr |
| Windows OS license fee (per vCPU) | Fargate (ECS) | NO — Not covered | 0% | Always billed at full rate |
| Ephemeral storage (above 20 GB free) | Fargate | NO — Not covered | 0% | $0.0000000308/GB-second |
| ARM/Graviton Fargate (vCPU) | Fargate ECS (not EKS) | YES — Covered | Up to ~52% (3-yr) | On-demand: $0.03238/vCPU-hr |
| Duration (GB-seconds) | Lambda | YES — Covered | Up to 17% | On-demand: $0.0000166667/GB-second |
| Provisioned Concurrency duration | Lambda | YES — Covered | Up to 17% | Both standard and ARM PC duration |
| Request charges | Lambda | NO — Not covered | 0% | $0.20/million requests — full rate always |
| Free tier (first 1M req/month) | Lambda | NO — Not applicable | Free (no SP needed) | Free tier persists regardless of SP |
| All EC2 instance compute | EC2 (all families) | YES — Covered | Up to 66% (3-yr) | Any family, region, OS, size, AZ |
| Spot Instance charges | EC2 Spot | NO — Not covered | 0% | Spot pricing already has deep discount |
| EC2 Dedicated Instance fees | EC2 | NO — Not covered | 0% | $2/hr Dedicated fee excluded |
Green = covered by Compute Savings Plan. Red = NOT covered, billed at standard rates regardless of commitment. Verify all rates at aws.amazon.com/savingsplans/compute-pricing — rates change frequently.
What the Fargate Coverage Actually Means for Your Bill
Fargate bills two mandatory components: vCPU-hours and memory GB-hours. Both are covered by the Compute Savings Plan at discounts up to approximately 52% on a 3-year term.
What is not covered is the Windows OS license fee — an additional per-vCPU-per-hour charge that applies when you run Windows containers on Fargate ECS. If you run exclusively Linux containers (the majority of Fargate workloads), this exclusion does not affect you at all. If you run Windows containers, your Fargate bill has two components: vCPU/memory at the Savings Plan rate, plus the Windows per-vCPU fee at full on-demand rate.
Ephemeral storage beyond the 20 GB free included with each task is also not covered. For most containerized workloads this is negligible. For tasks that mount significant temporary storage, account for it as an uncovered line item.
The practical takeaway: for standard Linux containerized workloads on ECS or EKS Fargate, the Compute Savings Plan covers essentially your entire Fargate compute bill. For Windows Fargate workloads, coverage is partial.
Fargate on Graviton (ARM): Fargate ARM pricing is approximately 20% cheaper than x86 on-demand. The Compute Savings Plan covers ARM Fargate vCPU and memory at the same discount tier as x86. Running ARM Fargate AND a Compute Savings Plan stacks both discounts — the ARM on-demand rate is already lower, and the SP discount applies on top of that lower rate. Source: aws.amazon.com/fargate/pricing. Verify — rates change.
What the Lambda Coverage Actually Means for Your Bill
This is where the biggest misunderstanding lives. Teams with Lambda-heavy architectures often assume their Compute Savings Plan is discounting their entire Lambda spend. It is not.
Lambda bills two components: duration (GB-seconds of compute) and requests ($0.20 per million). The Compute Savings Plan covers duration only. Requests are never covered by any Savings Plan.
The impact depends on your Lambda usage pattern. For functions with long-running executions (>1 second average), duration dominates the bill and the 17% discount is meaningful. For functions with many short invocations (sub-100ms), request charges can represent a large fraction of the total Lambda cost, and those are excluded.
A Real Example of What Gets Discounted
Suppose your Lambda functions run 100 million invocations per month, each averaging 500ms with 512MB memory. Duration cost: 100M x 0.5s x 0.5GB = 25,000,000 GB-seconds x $0.0000166667 = $416.67. Request cost: 100M requests x ($0.20/million) = $20.00. Total Lambda bill: $436.67.
With a Compute Savings Plan covering duration at 17% discount: duration at $346.94 (17% off) + requests unchanged at $20.00 = $366.94. The actual discount on your total Lambda bill is $69.73 — approximately 16%. If you had assumed 17% off the full $436.67, you would have projected $72.23 in savings. The difference is small here because requests are a minor component.
Now scale: 1 billion short (50ms) invocations per month with 128MB memory. Duration: 1B x 0.05s x 0.128GB = 6,400,000 GB-seconds x $0.0000166667 = $106.67. Requests: 1B x ($0.20/million) = $200.00. Total: $306.67. The Savings Plan covers $106.67 of duration at 17% = $18.13 savings. The request charges ($200) are untouched. Effective discount on total Lambda bill: 5.9%. For request-heavy Lambda workloads, the Savings Plan barely moves the needle.
Lambda’s 17% discount ceiling is the lowest of any service covered by Compute Savings Plans (EC2: up to 66%, Fargate: up to 52%). The Savings Plan still applies to Lambda automatically, but Lambda should not be the primary reason you buy a Compute Savings Plan. EC2 and Fargate coverage provide the meaningful financial return. Source: cloudkeeper.com/glossary/aws-compute-savings-plan and usage.ai pillar (verified from multiple sources).
Also read: How Compute Savings Plans work step-by-step — including how Lambda and Fargate charges are applied
Only the Compute Savings Plan Covers Lambda and Fargate — Not EC2 ISP
This is a point worth stating clearly because it affects which plan type you should buy.
EC2 Instance Savings Plans (the plan that saves up to 72%) do not cover Lambda or Fargate. Zero. If you buy an EC2 Instance Savings Plan and run Fargate tasks or Lambda functions, those charges receive no discount at all from your EC2 ISP commitment.
The Compute Savings Plan is the only AWS Savings Plan type that covers Lambda and Fargate. If your architecture uses either service significantly, that fact alone is a strong argument for Compute Savings Plans over EC2 Instance Savings Plans, regardless of the 6-percentage-point discount difference on EC2.
See the full Compute Savings Plan vs EC2 Instance Savings Plan comparison
How the Discount Is Applied Across All Three Services in One Hour
When you have a Compute Savings Plan and you are running EC2, Fargate, and Lambda in the same hour, AWS applies the discount in a specific order: highest discount percentage first.
In practice: EC2 usage typically has the highest Savings Plan discount percentage (up to 66%). Fargate is next (up to approximately 52%). Lambda duration is last (up to 17%). AWS works through your eligible usage from highest to lowest discount rate until your hourly commitment is consumed. The remaining usage bills at on-demand rates.
This ordering means if your commitment is small relative to your total usage, EC2 gets most of the discount benefit. Lambda is the last to benefit. For organizations whose primary goal is to discount Lambda costs, they need a large enough Compute Savings Plan commitment to cover the EC2 and Fargate usage first, then have remaining commitment to reach the Lambda duration charges.
How Usage.ai Handles Lambda and Fargate in Savings Plan Sizing
Most Savings Plan sizing tools calculate your commitment based on total compute spend. The problem with this for Lambda-heavy architectures: if 40% of your Lambda spend is request charges (excluded from Savings Plans), sizing off total Lambda cost over-sizes the commitment by that same 40%.
Usage.ai separates Lambda duration from Lambda requests when calculating the optimal commitment. It also separates Fargate vCPU/memory from Windows OS fees for Windows Fargate workloads. The commitment is sized against the actual coverable spend — not total spend — which produces a more accurate commitment level and avoids the over-commitment waste that comes from sizing against uncoverable charges.
The platform then purchases the commitment automatically, monitors utilization hourly, and adjusts quarterly. If a Lambda architecture changes (new functions launched, usage patterns shift), the commitment recalibrates. If any portion becomes underutilized, cashback in real money covers the unused portion. Fee: percentage of realized savings only.
Analyze your Lambda and Fargate coverage with Usage.ai — free savings estimate
Frequently Asked Questions
1. Does the AWS Compute Savings Plan cover Fargate?
Yes. Compute Savings Plans cover Fargate vCPU and memory charges for both ECS and EKS workloads, across all regions. The maximum discount on Fargate is approximately 52% on a 3-year plan. What is not covered: Windows OS license fees (the per-vCPU Windows charge), ephemeral storage above the 20 GB free tier per task, and Fargate Spot (which is already discounted separately). Source: docs.aws.amazon.com/savingsplans. Verify — rates change.
2. Does the AWS Compute Savings Plan cover Lambda?
Partially. Compute Savings Plans cover Lambda duration charges (measured in GB-seconds) and provisioned concurrency duration. The maximum discount is 17%. What is not covered: Lambda request charges ($0.20 per million requests). If your Lambda workload is request-heavy with many short invocations, the Savings Plan covers only the duration portion of your bill, which may be a small fraction of your total Lambda cost. Source: aws.amazon.com/savingsplans/compute-pricing.
3. How much does a Compute Savings Plan save on Fargate?
Up to approximately 52% on Fargate vCPU and memory on a 3-year All Upfront plan. A 1-year term saves less — approximately 20-35% depending on the specific configuration and region. The savings apply to the vCPU and memory components only. Windows OS fees and ephemeral storage above 20 GB are excluded. Verify current Fargate Savings Plan rates at aws.amazon.com/savingsplans/compute-pricing — rates change.
4. How much does a Compute Savings Plan save on Lambda?
Up to 17% on Lambda duration charges (GB-seconds). Lambda request charges receive no discount from any Savings Plan. For a Lambda workload spending $400/month on duration and $20/month on requests, the Compute Savings Plan saves up to $68/month (17% of $400). The request charges remain at $20/month. Effective discount on the total Lambda bill: approximately 15.6% in this example. Source: CloudKeeper AWS Compute Savings Plan guide, confirmed from AWS pricing documentation.
5. Does the EC2 Instance Savings Plan cover Fargate or Lambda?
No. EC2 Instance Savings Plans cover only EC2 instance usage within the committed family and region. Fargate and Lambda are not covered by EC2 Instance Savings Plans at all. The Compute Savings Plan is the only AWS Savings Plan type that includes Fargate and Lambda coverage. If you run significant Fargate or Lambda workloads, this is a key reason to choose Compute Savings Plans over EC2 Instance Savings Plans. Source: docs.aws.amazon.com/savingsplans/latest/userguide/plan-types.html.
6. Do Compute Savings Plans cover Fargate Spot?
No. Fargate Spot instances are not covered by Compute Savings Plans. Fargate Spot already carries discounts of up to 70% off standard Fargate pricing based on available spare capacity. Savings Plans apply to standard (on-demand) Fargate tasks only. If you use a mix of Fargate on-demand and Fargate Spot, the Savings Plan discount applies to the on-demand portion only. Source: aws.amazon.com/fargate/pricing.
7. How are Lambda charges applied within a Compute Savings Plan?
Lambda duration charges are applied last within a Compute Savings Plan — after EC2 (highest discount) and Fargate (next highest). AWS applies the commitment to usage with the highest savings rate first. Lambda’s 17% discount rate is the lowest of the three services, so it is the last to benefit from your commitment in any given hour. For Lambda to receive meaningful Savings Plan coverage, your commitment needs to be large enough to cover your EC2 and Fargate usage first.
