slate-cost

slate

You used AI to write your infrastructure. Now know exactly what it costs — before you deploy.

A zero-config CLI tool that reads your cdk synth output, calls the AWS Price List API for real prices, and produces a tiered cost estimate table across user growth scenarios.

Why

AI-assisted IaC development generates working infrastructure fast — but a single configuration decision (NAT Gateway, multi-AZ RDS, DynamoDB billing mode change) can shift monthly costs by hundreds of dollars silently. This tool makes that visible before you deploy.

How It Works

cdk synth → CDK Adapter → Classifier → AWS Price List API → Free Tier Deduction → Calculator → Output

• CDK Adapter — reads cdk.out/manifest.json + CloudFormation templates, normalizes resources
• Classifier — categorizes each resource as Fixed (exact price from plan) or Variable (scales with users)
• Pricing Client — calls AWS Price List API for region-accurate unit prices (never hardcoded)
• Free Tier — deducts AWS Free Tier allowances for accurate low-tier estimates
• Calculator — multiplies variable costs across user growth tiers
• Output — renders tier table, generates cost-profile.yaml, writes report JSON

Features

• Zero config — works immediately after cdk synth with no setup
• Real prices — all costs from AWS Price List API, never hardcoded
• Tiered output — costs shown across 0–100, 100–1k, 1k–10k, 10k–100k, 100k–1M users
• Free tier modeling — accurate $0 estimates at low usage (--no-free-tier to disable)
• Cost drift detection — diffs between runs show what changed and by how much
• Interactive wizard — guided CLI to fill in usage assumptions field by field
• CI/CD budget gate — exits code 1 if cost exceeds threshold
• MCP server — expose cost tools to AI editors (Kiro, VS Code, Continue)
• Multi-region — prices resources at their deployed region, not a default

Supported Resources

Fixed cost (priced exactly from plan): EC2, RDS, Aurora Provisioned, ECS Fargate, ElastiCache, NAT Gateway, OpenSearch, ALB/NLB, EKS Control Plane, MSK, WAF WebACL, Transfer Family, Route 53, Kinesis (provisioned)

Variable cost (scales with users, generates cost-profile.yaml fields): Lambda, API Gateway, DynamoDB, S3, CloudFront, Cognito, SQS, SNS, Step Functions, EventBridge, Secrets Manager, Bedrock, EKS Nodegroups, Aurora Serverless v2, WAF requests, Kinesis (on-demand), Transfer Family data

Quick Start

# Install
npm install --save-dev slate

# Run
npx cdk synth
npx slate estimate

# Interactive wizard to refine estimates
npx slate wizard

CLI Commands

Command	Description
slate estimate	Full pipeline — reads cdk.out/, outputs tier table
slate estimate --ci	CI mode — exits 1 on budget failure, includes drift
slate estimate --no-free-tier	Disable free tier deductions
slate estimate --json	Output as JSON
slate wizard	Interactive profile wizard
slate drift	Show drift between last two reports
slate init	Create config file with defaults

Configuration

slate.config.json:

{
  "region": "us-east-1",
  "iac": "cdk",
  "budget": {
    "tier": "1k-10k",
    "max_monthly_usd": 500,
    "use": "midpoint"
  }
}

The Precision Dial

cost-profile.yaml is generated with fields for your detected variable resources. Fill in what you know — leave blank what you don't.

Fields filled	Output
None	All variable costs shown as min–max range
Some	Filled fields exact, empty fields ranged
All	Every line item exact

Requirements

• Node.js 18+
• AWS CDK installed with cdk synth working
• IAM permission: pricing:GetProducts

Tech Stack

TypeScript, ESM, Commander, @aws-sdk/client-pricing, @inquirer/prompts, js-yaml, chalk, tsup, vitest

License

MIT