Gumroad

import fetch from 'isomorphic-unfetch';

export default async (_, res) => {
  const apiKey = process.env.GUMROAD_API_KEY;
  const productId = 'sDpG';
  const response = await fetch(
    `https://api.gumroad.com/v2/products/${productId}`,
    {
      headers: {
        Authorization: `Bearer ${apiKey}`,
        'Content-Type': 'application/json'
      },
      method: 'GET'
    }
  );

  const { product } = await response.json();
  const sales = product.sales_usd_cents / 100;

  return res.status(200).json({ sales });
};

Usage

First, create a Gumroad account. Then, navigate to the Applications tab and create a new app.

Make note of your "Application Secret". Since we're communicating server to server, we only need the secret.

To securely access the API, we need to include the secret with each request. We also do not want to commit secrets to git. Thus, we should use an environment variable. Learn how to add environment variables in Vercel.