Skip to main content

​
Prerequisites

  • A Fluxrate account (sign up here)
  • Your backend can make HTTP requests (any language)

​
Step 1 — Create a Meter

A meter defines what usage you want to track. Head to Dashboard → Features and create your first meter feature, or use the API: 
curl -X POST https://api.fluxrate.co/api/v1/features \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "name": "API Calls",
    "lookup_key": "api_calls",
    "type": "meter",
    "meter_name": "api_calls",
    "property_name": "call_count",
    "aggregation_type": "SUM",
    "unit": "calls"
  }'
Note the meter_token from the response — you’ll need it to send usage events.

​
Step 2 — Create a Plan

Plans define what customers pay. Create a usage-based plan that charges per API call: 
curl -X POST https://api.fluxrate.co/api/v1/plans \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "name": "Starter",
    "lookup_id": "starter",
    "type": "USAGE",
    "billing_interval": "month",
    "currency": "USD"
  }'
Then add the charge to the plan: 
curl -X POST https://api.fluxrate.co/api/v1/plans/<plan_id>/charges \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "type": "USAGE",
    "meter_id": "<your_meter_id>",
    "unit_price": 0.001,
    "display_name": "API Call Charge"
  }'

​
Step 3 — Create a Customer

curl -X POST https://api.fluxrate.co/api/v1/customers \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "name": "Acme Corp",
    "email": "billing@acme.com",
    "external_id": "acme-corp-001"
  }'

​
Step 4 — Subscribe the Customer

curl -X POST https://api.fluxrate.co/api/v1/subscriptions \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "customer_id": "<customer_id>",
    "plan_id": "<plan_id>",
    "billing_interval": "month",
    "start_date": "2025-01-01T00:00:00Z"
  }'

​
Step 5 — Generate an API Key

Go to Dashboard → API Keys and create a key with usage.write scope. This key is used to send usage events from your backend. 
curl -X POST https://api.fluxrate.co/api/v1/api-keys \
  -H "Content-Type: application/json" \
  -H "Cookie: access_token=<your_token>" \
  -d '{
    "name": "Production SDK Key",
    "scopes": ["usage.write"]
  }'
Copy the returned API key — it is shown only once.

​
Step 6 — Track Usage Events

Send usage events from your backend using the SDK endpoint. Authenticate with your API key: 
curl -X POST https://api.fluxrate.co/api/v1/sdk/track \
  -H "Content-Type: application/json" \
  -H "X-API-Key: org_live_<your_key>" \
  -d '{
    "meter_token": "<meter_token>",
    "customer_external_id": "acme-corp-001",
    "quantity": 150,
    "idempotency_key": "req_unique_abc123"
  }'
Always pass an idempotency_key to prevent duplicate events if your request retries.

​
Step 7 — Wait for the Invoice

When the subscription billing period ends, Fluxrate automatically:
  1. Calculates usage from all tracked events
  2. Creates a DRAFT invoice
  3. Waits 1 hour (grace period) for manual review
  4. Finalizes the invoice to OPEN status
  5. Emails the customer (if SMTP is configured)
You can also manually generate an invoice at any time: 
curl -X POST https://api.fluxrate.co/api/v1/subscriptions/<subscription_id>/generate-invoice \
  -H "Cookie: access_token=<your_token>"

​
You’re Ready! 🎉

Explore Plans

Fixed, usage, and hybrid pricing

Usage Analytics

Query and visualize usage data

API Reference

Full endpoint documentation