System Design Explained in 1 Hour

I walk through the system design behind Hachisu, a Bitcoin payment processor mobile app. I break down the full architecture from the ground up, including product requirements, core entities, API/interface design, high-level system design, and deeper technical decisions around wallets, stores, payments, invoices, and merchant workflows. This is a practical system design walkthrough for anyone interested in building real-world fintech, Bitcoin, Web3, or mobile payment infrastructure. 00:00: Functional and Non-functional Requirements 49:45: Core App Entities 50:27: APIs/Interface 51:58: Data Flow 53:01: High Level Design and Deep Dives