SaaS API Monetization: Usage-Based Billing

TL;DR: Usage-based billing (metered billing) charges customers based on API consumption — requests, storage, compute time, or users. Stripe's metered billing integration with TanStack Start makes this straightforward. This guide covers metering architecture, pricing models (per-request, tiered, overage), and developer portal design.

Introduction

Usage-based billing aligns your revenue with the value customers receive. Small users pay little; power users pay more. This model is standard for API products (Twilio, Stripe, OpenAI) and increasingly adopted by SaaS platforms.

Metering Architecture

// API usage metering middleware
export const meterApiUsage = defineMiddleware({
  before: async ({ request, context }) => {
    const apiKey = request.headers.get('x-api-key')
    const user = await getUserByApiKey(apiKey)

    // Record usage event
    context.metering = {
      userId: user.id,
      endpoint: request.url,
      timestamp: Date.now(),
    }
  },
  after: async ({ context }) => {
    // Increment usage counter in D1
    await db.insertInto('api_usage').values({
      user_id: context.metering.userId,
      endpoint: context.metering.endpoint,
      timestamp: context.metering.timestamp,
    }).execute()
  },
})

Pricing Models

Stripe Metered Billing

import Stripe from 'stripe'

// Report usage to Stripe
await stripe.subscriptionItems.createUsageRecord(
  subscriptionItemId,
  {
    quantity: apiCalls,
    timestamp: 'now',
    action: 'increment',
  }
)

Conclusion

Usage-based billing aligns pricing with value. The metering infrastructure — track usage, report to Stripe, display in a dashboard — is straightforward with TanStack Start server functions and Stripe's metered billing API. For a complete billing strategy, see our Stripe Billing guide and SaaS Pricing Tier Strategy.