[BE] Sang Hoang ( hoangvansang846@gmail.com)

.gitignore

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+node_modules/
+dist/
+build/
+coverage/
+*.tsbuildinfo
+
+.env
+.env.local
+.env.*.local
+
+.DS_Store
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*

README copy.md

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+# My Challenge
+
+This workspace contains my own solutions for:
+
+- `problem4`: three TypeScript implementations of sum-to-n
+- `problem5`: a TypeScript Express + PostgreSQL CRUD API with a concurrency-safe increment endpoint using TypeORM pessimistic locking
+- `problem6`: an implementation-ready architecture package for a real-time scoreboard using PostgreSQL, transactional outbox, CDC/Kafka, Redis projections, and live updates
+
+## Scripts
+
+From this directory:
+
+```bash
+npm install
+npm run test:problem4
+npm run dev:problem5
+npm run test:problem5
+```
+
+## Notes
+
+- Problem 5 expects PostgreSQL for both development and integration tests.
+- See `src/problem5/README.md` for database configuration and the locking test design.
+- Problem 6 is a documentation and system-design deliverable under `src/problem6/`.