Solution Yape Challenge - Paolo Rossi

SOLUTION.md

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+# Solution
+
+## Set up
+
+1. Start the docker container with the necessary infrastructure:
+   ```bash
+   docker-compose up
+   ```
+
+2. Create the environment files:
+   - For transactions-ms, create a .env file in the root directory with the following content:
+     ```dotenv
+     TRANSACTIONS_MS_PORT=3000
+
+     DATABASE_URL=postgresql://postgres:postgres@localhost:5432/postgres?schema=public
+
+     KAFKA_BROKERS=localhost:9092
+     KAFKA_GROUP_ID=transactions-group
+
+     REDIS_HOST=localhost
+     REDIS_PORT=6379
+     ```
+   - For anti-fraud-ms, create a .env file in the root directory with the following content:
+     ```dotenv
+     KAFKA_BROKERS=localhost:9092
+     KAFKA_GROUP_ID=anti-fraud-group
+     ```
+
+3. Install the dependencies and start the development server for each app: 
+   ```bash
+   pnpm install
+   pnpm dev
+   ```
+
+
+4. Run the Prisma migrations for transactions-ms:
+   ```bash
+   pnpm db:migrate
+   ```
+
+5. The project is now set up and ready to use. You can play with the Apollo Sandbox at http://localhost:3000/graphql
+
+## Assumptions
+
+- The `transaction-ms` service is in charge of creating the unique ID for a transaction, called "transactionExternalId", so this service is not responsible for checking for duplicate requests when creating new transactions.
+
+- The Transaction Type is obtained with a constant object using the tranferTypeId as a key: 1 corresponds to "DEBIT", and 2 corresponds to "CREDIT"
+
+## Tech Decisions
+
+1. **Use of GraphQL instead of a REST API**
+
+   - **Efficient Data Fetching**: Clients can specify exactly what data they require, reducing over and under fetching of data, minimizing the amount of data transferred over the network.
+
+   - **Strongly Typed Schema**: GraphQL's schema provides a clear contract between the client and server, making it easier to understand the data structure and reducing the likelihood of errors.
+
+2. **Use of Prisma ORM**
+
+   - **Type Safety**: With TypeScript support, Prisma ensures that queries are type-checked at compile time, reducing runtime errors and improving developer productivity.
+
+   - **Efficient Querying**: Prisma generates optimized SQL queries, which can significantly enhance performance when dealing with large datasets and high-frequency transactions.
+
+3. **Retries in Transaction Service**
+
+   Implementing retries is essential for ensuring reliability and consistency in high-volume scenarios where network issues or temporary database unavailability can occur. Retries help mitigate these transient errors, ensuring that operations are completed successfully.
+
+4. **Redis Cache**
+
+   Utilizing Redis as a caching layer is advantageous for performance and scalability in high-volume scenarios; giving **fast data access** and **reduding database load**.
+
+## Possible Improvements
+
+- **Database Replication**: Implement leader-follower replication to distribute read loads across multiple replicas, enhancing read performance and availability.
+
+- **Load Balancing**: Use a load balancer to distribute incoming requests evenly across multiple application instances, preventing any single instance from becoming a bottleneck.
+
+- **Connection Pooling**: Implement connection pooling to manage database connections efficiently, reducing the overhead of establishing new connections for each request.
+
+- **Monitoring and Alerts**: Set up monitoring tools to track performance metrics and establish alerts for unusual spikes in traffic or errors, enabling proactive management of high-volume scenarios.
+
+- **Real-time Capabilities**: GraphQL supports subscriptions, allowing clients to receive real-time updates. In that way, clients will always have the most current information without needing to poll the server.

anti-fraud-ms/package.json

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+{
+  "name": "anti-fraud-ms",
+  "version": "1.0.0",
+  "scripts": {
+    "build": "nest build",
+    "dev": "nest start --watch",
+    "start": "node ."
+  },
+  "dependencies": {
+    "@nestjs/common": "^10.3.7",
+    "@nestjs/core": "^10.3.7",
+    "@nestjs/microservices": "^10.4.3",
+    "class-transformer": "^0.5.1",
+    "class-validator": "^0.14.1",
+    "kafkajs": "^2.2.4"
+  },
+  "devDependencies": {
+    "@nestjs/cli": "^10.4.5",
+    "@types/node": "^20.12.7",
+    "typescript": "^5.4.5"
+  }
+}