Merchant Bookkeeping Service: Transaction Recording and Balance Retrieval

stripe Design and implement a bookkeeping service that records money sent and received on behalf of a merchant, and allows retrieving the account balance for a given merchant. Requirements: Implement an API to record money sent or received on behalf of a merchant. Implement an API to get the account balance for a given merchant. Consider how to build the system, including data storage, system architecture, and methods to ensure data consistency. Please detail each API's functionality and parameters, and explain your design choices. Example Input merchant123 100 USD txn001