Building a Sponsor System with Stripe

Why we built self-serve sponsoring

Manual sponsor deals don't scale. We wanted a system where anyone could book a banner slot, pay, and go live without human intervention.

Architecture overview

The system has three core components:

• Calendar picker for date selection with availability checks
• Stripe Checkout for secure payment processing
• Webhook handler for automatic activation on payment success

Dynamic pricing with volume discounts

We implemented a progressive discount system. The longer the campaign, the better the daily rate:

function calculatePrice(days: number): number {
  const BASE_PRICE = 300 // $3.00 per day in cents
  const MAX_DISCOUNT = 0.30
  const MAX_DAYS = 30

  const ratio = Math.min(days, MAX_DAYS) / MAX_DAYS
  const discount = ratio * MAX_DISCOUNT
  const dailyPrice = BASE_PRICE * (1 - discount)

  return Math.round(dailyPrice * days)
}

A 7-day campaign costs $2.79/day while a 30-day campaign drops to $2.10/day.

Handling the Stripe webhook

The webhook endpoint verifies the signature and activates the campaign:

export async function POST(req: Request) {
  const body = await req.text()
  const sig = req.headers.get("stripe-signature")!

  const event = stripe.webhooks.constructEvent(
    body,
    sig,
    process.env.STRIPE_WEBHOOK_SECRET!
  )

  if (event.type === "checkout.session.completed") {
    const session = event.data.object
    await activateSponsorCampaign(session.metadata)
  }

  return new Response("ok")
}

Always verify the webhook signature. Never trust the payload without it.

The full source code is available in the template repository.