plaid-fintech

# Plaid Fintech Expert patterns for Plaid API integration including Link token flows, transactions sync, identity verification, Auth for ACH, balance checks, webhook handling, and fintech compliance best practices. ## Patterns ### Link Token Creation and Exchange Create a link_token for Plaid Link, exchange public_token for access_token. Link tokens are short-lived, one-time use. Access tokens don't expire but may need updating when users change passwords. // server.ts - Link token creation endpoint import { Configuration, PlaidApi, PlaidEnvironments, Products, CountryCode } from 'plaid'; const configuration = new Configuration({ basePath: PlaidEnvironments[process.env.PLAID_ENV || 'sandbox'], baseOptions: { headers: { 'PLAID-CLIENT-ID': process.env.PLAID_CLIENT_ID, 'PLAID-SECRET': process.env.PLAID_SECRET, }, }, }); const plaidClient = new PlaidApi(configuration); // Create link token for new user app.post('/api/plaid/create-link-token', async (req, res) => { const { userId } = req.body; try { const response = await plaidClient.linkTokenCreate({ user: { client_user_id: userId, // Your internal user ID }, client_name: 'My Finance App', products: [Products.Transactions], country_codes: [CountryCode.Us], language: 'en', webhook: 'https://yourapp.com/api/plaid/webhooks', // Request 180 days for recurring transactions transactions: { days_requested: 180, }, ...