Enterprise Wallet & Credit-Deduction Architecture

Core reference for building production-grade digital wallet systems under high concurrency. Covers PostgreSQL schema design, concurrency controls, fault tolerance, security, and load testing.

When to load supplementary files:

• Choosing a locking strategy → see LOCKING-STRATEGIES.md
• Implementing Saga / Outbox → see SAGA-OUTBOX.md
• Security & Idempotency middleware → see SECURITY.md
• Load testing with k6 → see LOAD-TESTING.md
• Full ledger schema (DDL) → see SCHEMA.md

The 15 Financial Mishaps — Quick Reference