Financial Custody: Managing Balance and Portfolio with Eventual Consistency

Based on your detailed documentation of the wallet module development, here are some key takeaways and next steps:

1. Module Structure and Dependencies:

   • The trading-broker-wallet module is a Spring Boot application with Kafka consumer functionality.
   • It depends on common modules for shared code and Flyway for database migrations.

2. Database Schema Changes:

   • Added new columns to the wallet_transactions table: transaction_type, order_id.
   • Created an index on (user_id, transaction_type) for performance optimization.
   • Added a unique constraint on (order_id, transaction_type) for idempotency.

3. Business Logic:

   • Implemented methods for depositing funds, withdrawing available balance, and calculating the user's total equity.
   • Created REST API endpoints to interact with the wallet functionality.
   • Developed logic to process order events from Kafka, updating balances and positions accordingly.

4. Critical Bugs Fixed:

   • Ensured proper initialization of blockedBalance for new accounts.
   • Corrected validation logic for withdrawals to only check available balance.
   • Fixed incorrect handling of sell orders in position updates.
   • Improved error handling in the Kafka

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