Data model for a Venmo-style P2P payment system

Design the data model for a peer-to-peer payment system similar to Venmo. User A wants to pay User B.
Each user has an internal account/debit balance on the platform and may also have one or more external
bank accounts linked. Payments that involve a bank have a settlement delay of roughly two days. Define the
tables, their attributes, and the relationships needed to support the money-movement flows. Walk through
how the model represents each scenario:

• (a) A pays B entirely from internal balance;
• (b) A pays B by pulling from an external bank into the platform;
• (c) bank transfer with delayed (~2-day) settlement;
• (d) mixed funding — part internal balance, part external bank.