feat: implement event-driven architecture with Kafka, idempotency, and Redis integration

.vscode/settings.json

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+{
+    "prisma.pinToPrisma6": true
+}

README.md

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-# Yape Code Challenge :rocket:
+# 🏦 Transaction Processing System (Code Challenge)
 
-Our code challenge will let you marvel us with your Jedi coding skills :smile:. 
+This project is a solution to the Yape Code Challenge.
 
-Don't forget that the proper way to submit your work is to fork the repo and create a PR :wink: ... have fun !!
+## 📌 Overview
 
-- [Problem](#problem)
-- [Tech Stack](#tech_stack)
-- [Send us your challenge](#send_us_your_challenge)
+This project implements a simple **event-driven architecture** using Node.js, Kafka, and PostgreSQL.
 
-# Problem
+The system processes financial transactions and validates them through an anti-fraud microservice.
 
-Every time a financial transaction is created it must be validated by our anti-fraud microservice and then the same service sends a message back to update the transaction status.
-For now, we have only three transaction statuses:
+---
 
-<ol>
-  <li>pending</li>
-  <li>approved</li>
-  <li>rejected</li>  
-</ol>
+## 🧱 Architecture
 
-Every transaction with a value greater than 1000 should be rejected.
+The solution is composed of two microservices:
 
-```mermaid
-  flowchart LR
-    Transaction -- Save Transaction with pending Status --> transactionDatabase[(Database)]
-    Transaction --Send transaction Created event--> Anti-Fraud
-    Anti-Fraud -- Send transaction Status Approved event--> Transaction
-    Anti-Fraud -- Send transaction Status Rejected event--> Transaction
-    Transaction -- Update transaction Status event--> transactionDatabase[(Database)]
-```
+* **transaction-service**
+
+  * Creates transactions
+  * Stores them in PostgreSQL
+  * Publishes events to Kafka
+  * Consumes validation results
+
+* **anti-fraud-service**
+
+  * Consumes transaction events
+  * Applies validation rules
+  * Publishes transaction status updates
+
+---
+
+## 🔄 Flow
 
-# Tech Stack
+1. A transaction is created via API
+2. It is stored with status `pending`
+3. An event `transaction.created` is sent to Kafka
+4. Anti-fraud service consumes the event
+5. Applies rule:
 
-<ol>
-  <li>Node. You can use any framework you want (i.e. Nestjs with an ORM like TypeOrm or Prisma) </li>
-  <li>Any database</li>
-  <li>Kafka</li>    
-</ol>
+   * If value > 1000 → `rejected`
+   * Else → `approved`
+6. Publishes `transaction.validated`
+7. Transaction service consumes and updates status
 
-We do provide a `Dockerfile` to help you get started with a dev environment.
+---
 
-You must have two resources:
+## 🧪 API Endpoints
 
-1. Resource to create a transaction that must containt:
+### ➤ Create Transaction
+
+**POST /transactions**
 
 ```json
 {
-  "accountExternalIdDebit": "Guid",
-  "accountExternalIdCredit": "Guid",
+  "accountExternalIdDebit": "string",
+  "accountExternalIdCredit": "string",
   "tranferTypeId": 1,
   "value": 120
 }
 ```
 
-2. Resource to retrieve a transaction
+**Response:**
 
 ```json
 {
-  "transactionExternalId": "Guid",
+  "transactionId": "uuid",
+  "status": "pending"
+}
+```
+
+---
+
+### ➤ Get Transaction
+
+**GET /transactions/:id**
+
+**Response:**
+
+```json
+{
+  "transactionExternalId": "uuid",
   "transactionType": {
-    "name": ""
+    "name": "transfer"
   },
   "transactionStatus": {
-    "name": ""
+    "name": "approved"
   },
   "value": 120,
-  "createdAt": "Date"
+  "createdAt": "date"
 }
 ```
 
-## Optional
+---
+
+## ⚙️ Tech Stack
+
+* Node.js (NestJS)
+* PostgreSQL (Prisma ORM)
+* Kafka (KafkaJS)
+* Docker
+
+---
+
+## 🚀 How to Run
+
+### 1. Start infrastructure
+
+```bash
+docker-compose up -d
+```
+
+---
+
+### 2. Run transaction-service
+
+```bash
+cd transaction-service
+npm install
+npm run start:dev
+```
+
+---
+
+### 3. Run anti-fraud-service
+
+```bash
+cd anti-fraud-service
+npm install
+npm run start:dev
+```
+
+---
+
+## 📡 Kafka Topics
+
+* `transaction.created`
+* `transaction.validated`
+
+---
+
+## 🧠 Design Decisions
+
+* Event-driven architecture for decoupling services
+* Asynchronous validation to improve scalability
+* Prisma ORM for type-safe database access
+* Kafka for reliable message delivery
+
+---
+
+## ⚡ Scalability Considerations
+
+To handle high load scenarios:
+
+* Horizontal scaling of consumers (Kafka consumer groups)
+* Partitioned topics for parallel processing
+* Database indexing on transaction ID
+* Potential use of caching (e.g., Redis)
+
+---
 
-You can use any approach to store transaction data but you should consider that we may deal with high volume scenarios where we have a huge amount of writes and reads for the same data at the same time. How would you tackle this requirement?
+## ✅ Status
 
-You can use Graphql;
+✔ Transaction creation
+✔ Anti-fraud validation
+✔ Kafka communication
+✔ Transaction status update
+✔ Transaction query by ID
 
-# Send us your challenge
+---
 
-When you finish your challenge, after forking a repository, you **must** open a pull request to our repository. There are no limitations to the implementation, you can follow the programming paradigm, modularization, and style that you feel is the most appropriate solution.
+## 👨‍💻 Author
 
-If you have any questions, please let us know.
+Christian Pulache

anti-fraud-service/.eslintrc.js

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+module.exports = {
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    project: 'tsconfig.json',
+    tsconfigRootDir: __dirname,
+    sourceType: 'module',
+  },
+  plugins: ['@typescript-eslint/eslint-plugin'],
+  extends: [
+    'plugin:@typescript-eslint/recommended',
+    'plugin:prettier/recommended',
+  ],
+  root: true,
+  env: {
+    node: true,
+    jest: true,
+  },
+  ignorePatterns: ['.eslintrc.js'],
+  rules: {
+    '@typescript-eslint/interface-name-prefix': 'off',
+    '@typescript-eslint/explicit-function-return-type': 'off',
+    '@typescript-eslint/explicit-module-boundary-types': 'off',
+    '@typescript-eslint/no-explicit-any': 'off',
+  },
+};

anti-fraud-service/.gitignore

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+# compiled output
+/dist
+/node_modules
+
+# Logs
+logs
+*.log
+npm-debug.log*
+pnpm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+
+# OS
+.DS_Store
+
+# Tests
+/coverage
+/.nyc_output
+
+# IDEs and editors
+/.idea
+.project
+.classpath
+.c9/
+*.launch
+.settings/
+*.sublime-workspace
+
+# IDE - VSCode
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json

anti-fraud-service/.prettierrc

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+{
+  "singleQuote": true,
+  "trailingComma": "all"
+}

anti-fraud-service/README.md

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+<p align="center">
+  <a href="http://nestjs.com/" target="blank"><img src="https://nestjs.com/img/logo-small.svg" width="200" alt="Nest Logo" /></a>
+</p>
+
+[circleci-image]: https://img.shields.io/circleci/build/github/nestjs/nest/master?token=abc123def456
+[circleci-url]: https://circleci.com/gh/nestjs/nest
+
+  <p align="center">A progressive <a href="http://nodejs.org" target="_blank">Node.js</a> framework for building efficient and scalable server-side applications.</p>
+    <p align="center">
+<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/v/@nestjs/core.svg" alt="NPM Version" /></a>
+<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/l/@nestjs/core.svg" alt="Package License" /></a>
+<a href="https://www.npmjs.com/~nestjscore" target="_blank"><img src="https://img.shields.io/npm/dm/@nestjs/common.svg" alt="NPM Downloads" /></a>
+<a href="https://circleci.com/gh/nestjs/nest" target="_blank"><img src="https://img.shields.io/circleci/build/github/nestjs/nest/master" alt="CircleCI" /></a>
+<a href="https://coveralls.io/github/nestjs/nest?branch=master" target="_blank"><img src="https://coveralls.io/repos/github/nestjs/nest/badge.svg?branch=master#9" alt="Coverage" /></a>
+<a href="https://discord.gg/G7Qnnhy" target="_blank"><img src="https://img.shields.io/badge/discord-online-brightgreen.svg" alt="Discord"/></a>
+<a href="https://opencollective.com/nest#backer" target="_blank"><img src="https://opencollective.com/nest/backers/badge.svg" alt="Backers on Open Collective" /></a>
+<a href="https://opencollective.com/nest#sponsor" target="_blank"><img src="https://opencollective.com/nest/sponsors/badge.svg" alt="Sponsors on Open Collective" /></a>
+  <a href="https://paypal.me/kamilmysliwiec" target="_blank"><img src="https://img.shields.io/badge/Donate-PayPal-ff3f59.svg"/></a>
+    <a href="https://opencollective.com/nest#sponsor"  target="_blank"><img src="https://img.shields.io/badge/Support%20us-Open%20Collective-41B883.svg" alt="Support us"></a>
+  <a href="https://twitter.com/nestframework" target="_blank"><img src="https://img.shields.io/twitter/follow/nestframework.svg?style=social&label=Follow"></a>
+</p>
+  <!--[![Backers on Open Collective](https://opencollective.com/nest/backers/badge.svg)](https://opencollective.com/nest#backer)
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+
+## Description
+
+[Nest](https://github.com/nestjs/nest) framework TypeScript starter repository.
+
+## Installation
+
+```bash
+$ npm install
+```
+
+## Running the app
+
+```bash
+# development
+$ npm run start
+
+# watch mode
+$ npm run start:dev
+
+# production mode
+$ npm run start:prod
+```
+
+## Test
+
+```bash
+# unit tests
+$ npm run test
+
+# e2e tests
+$ npm run test:e2e
+
+# test coverage
+$ npm run test:cov
+```
+
+## Support
+
+Nest is an MIT-licensed open source project. It can grow thanks to the sponsors and support by the amazing backers. If you'd like to join them, please [read more here](https://docs.nestjs.com/support).
+
+## Stay in touch
+
+- Author - [Kamil Myśliwiec](https://kamilmysliwiec.com)
+- Website - [https://nestjs.com](https://nestjs.com/)
+- Twitter - [@nestframework](https://twitter.com/nestframework)
+
+## License
+
+Nest is [MIT licensed](LICENSE).

anti-fraud-service/nest-cli.json

@@ -0,0 +1,8 @@
+{
+  "$schema": "https://json.schemastore.org/nest-cli",
+  "collection": "@nestjs/schematics",
+  "sourceRoot": "src",
+  "compilerOptions": {
+    "deleteOutDir": true
+  }
+}