Building an Expert Marketplace with CallPayMin

Overview

CallPayMin is perfect for building expert marketplaces - platforms that connect professionals (experts) with people seeking advice (clients). This guide covers the architecture and API flows you'll need.

Marketplace Architecture

Key Components

Experts (Supply)

• Profile & bio
• Rate per minute
• Availability calendar
• Expertise categories
• Stripe Connect account

Clients (Demand)

• Account balance
• Payment method
• Booking history
• Saved experts

Step 1: User Registration

Create users in CallPayMin when they sign up on your platform:

Create an Expert

// When an expert signs up
const expert = await client.users.create({
  externalId: 'your-db-user-id',
  role: 'expert',
  email: 'expert@example.com',
  name: 'Dr. Jane Smith',
  profile: {
    title: 'Startup Advisor',
    bio: '20 years experience in tech startups...',
    categories: ['business', 'startups', 'fundraising'],
  },
  billing: {
    ratePerMinute: 5.00, // $5/minute
    currency: 'usd',
  },
});

Create a Client

// When a client signs up
const client = await client.users.create({
  externalId: 'your-db-user-id',
  role: 'quester',
  email: 'client@example.com',
  name: 'John Doe',
});

// Add initial balance (if Self-Managed)
// Or set up payment method (if Fully Managed)

Step 2: Booking Flow

When a client wants to book a call with an expert:

Create a Call

// Create the call
const call = await client.calls.create({
  expertId: 'expert_123',
  questerId: 'client_456',
  type: 'video',
  scheduledAt: '2025-01-20T14:00:00Z', // Optional: for scheduled calls
  billingMode: 'per_minute',
  settings: {
    recording: true,
    aiSummary: true,
    maxDuration: 60, // 60 minutes max
  },
});

// Send join links
sendEmail(expert.email, {
  subject: 'Upcoming Call',
  joinUrl: call.expertJoinUrl,
});

sendEmail(client.email, {
  subject: 'Your Call is Confirmed',
  joinUrl: call.questerJoinUrl,
});

Step 3: Handle Webhooks

Listen for events to update your platform in real-time:

Webhook Handler

app.post('/webhooks/callpaymin', (req, res) => {
  const event = req.body;

  switch (event.type) {
    case 'call.started':
      // Update your UI to show call is active
      notifyUser(event.data.questerId, 'Call started!');
      break;

    case 'call.ended':
      // Update call record in your database
      updateCallRecord(event.data.callId, {
        duration: event.data.duration,
        cost: event.data.cost,
      });
      break;

    case 'summary.ready':
      // AI summary is available
      const summary = event.data.summary;
      sendEmail(event.data.questerId, {
        subject: 'Your Call Summary',
        body: summary.keyPoints,
      });
      break;

    case 'user.balance_low':
      // Prompt user to add funds
      sendEmail(event.data.userId, {
        subject: 'Low Balance Alert',
        body: 'Add funds to continue booking calls.',
      });
      break;
  }

  res.status(200).json({ received: true });
});

Revenue Model

With CallPayMin, you can implement various revenue models:

Platform Fee

Take a percentage of each call. E.g., expert charges $5/min, you keep 20% ($1/min).

Subscription

Charge experts a monthly fee for premium placement and features.

Credits

Sell credit packages at a markup. Users buy credits, you pocket the margin.

Freemium

Offer free minutes, charge for premium features like recordings or AI summaries.

Next Steps

Ready to build your marketplace? Check out the API documentation and sign up for a free account to get started.