This comprehensive tutorial demonstrates how developers can build a complete card payment system using Blnk Finance, an open-source ledger for fintech products. The guide explains the critical two-step payment process: authorization (holding funds) and settlement (moving money). Using a practical e-commerce demo, you'll learn to implement core ledger concepts including ledgers for organizing accounts, identities for customer representation, and balances for card accounts.

The tutorial covers the inflight transaction feature, which is essential for managing payment holds and settlements. Key technical implementations include setting up Blnk Core with Docker, initializing the TypeScript SDK, creating server actions for card account creation, authorizing payments with inflight transactions, and settling transactions through commit or void operations. The guide also walks through building a React frontend with a merchant dashboard for managing pending orders.

By following this step-by-step process, developers can understand and implement the financial integrity mechanisms that power modern payment systems.