init

Author: llxff

.env.example

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+# Database
+DATABASE_URL=postgresql://postgres:postgres@localhost:5432/hiring_task_dev
+
+# RabbitMQ
+RABBITMQ_URL=amqp://guest:guest@localhost:5672
+
+# External Service
+EXTERNAL_SERVICE_API_KEY=your_api_key_here
+
+# JWT
+JWT_SECRET=your_jwt_secret_here

.eslintrc.js

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+module.exports = {
+  parser: "@typescript-eslint/parser",
+  extends: [
+    "eslint:recommended",
+    "plugin:import/recommended",
+    "plugin:import/typescript",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended",
+    "plugin:prettier/recommended",
+  ],
+  plugins: ["import", "@typescript-eslint"],
+  parserOptions: {
+    sourceType: "module",
+    ecmaVersion: 2018,
+  },
+  env: {
+    es6: true,
+    node: true,
+  },
+  rules: {
+    "import/no-named-as-default-member": "off",
+    "import/no-named-as-default": "off",
+    "@typescript-eslint/no-explicit-any": ["off"],
+    "@typescript-eslint/ban-ts-comment": "off",
+    "@typescript-eslint/no-non-null-assertion": "off",
+    "no-duplicate-imports": "error",
+    "import/no-useless-path-segments": [
+      "error",
+      {
+        noUselessIndex: true,
+      },
+    ],
+    "import/order": "error",
+    "@typescript-eslint/no-unused-vars": ["error", { argsIgnorePattern: "^_" }],
+    "arrow-body-style": ["error", "as-needed"],
+    "import/no-unresolved": "off",
+  },
+  settings: {
+    "import/parsers": {
+      "@typescript-eslint/parser": [".ts", ".tsx"],
+    },
+    "import/resolver": {
+      node: {
+        extensions: [".ts", ".tsx", ".js", ".jsx", ".vue"],
+      },
+    },
+  },
+}

.prettierrc.yml

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+semi: false
+singleQuote: false
+tabWidth: 2
+quoteProps: "consistent"
+printWidth: 120

README.md

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+# Code Review Challenge
+
+## Overview
+
+This is a code review challenge designed to evaluate your understanding of complex distributed systems, database internals, and system design. The project represents a simplified e-commerce system with multiple services handling orders, payments, and analytics.
+
+The system is designed to work with both MySQL and PostgreSQL databases, which introduces interesting challenges due to their different behaviors and characteristics.
+
+## Challenge Description
+
+Your task is to review this codebase and identify potential issues, problems, and areas for improvement. The codebase intentionally contains various issues that a senior engineer might encounter in real-world distributed systems.
+
+## Evaluation Criteria
+
+Strong candidates will:
+
+- Identify significant architectural and design issues
+- Understand database internals and their implications
+- Recognize distributed systems challenges
+- Propose practical, well-reasoned solutions
+- Consider trade-offs in their recommendations
+- Propose systematic approaches to preventing similar issues

db/schema.sql

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+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+-- Function to update timestamp
+CREATE OR REPLACE FUNCTION update_updated_at_column()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = CURRENT_TIMESTAMP;
+    RETURN NEW;
+END;
+$$ language 'plpgsql';
+
+CREATE TABLE users (
+    id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    name VARCHAR(255) NOT NULL,
+    email VARCHAR(255) NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT users_email_unique UNIQUE (email)
+);
+
+CREATE INDEX users_email_idx ON users(email);
+
+CREATE TABLE products (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(255) NOT NULL,
+    price DECIMAL(10,2) NOT NULL CHECK (price >= 0),
+    stock INTEGER NOT NULL CHECK (stock >= 0),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE TABLE orders (
+    id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    user_id UUID NOT NULL,
+    total_amount DECIMAL(10,2) NOT NULL CHECK (total_amount >= 0),
+    status INTEGER NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (user_id) REFERENCES users(id)
+);
+
+CREATE INDEX orders_user_id_idx ON orders(user_id);
+CREATE INDEX orders_status_idx ON orders(status);
+
+CREATE TABLE order_items (
+    id SERIAL PRIMARY KEY,
+    order_id UUID NOT NULL,
+    product_id INTEGER NOT NULL,
+    quantity INTEGER NOT NULL CHECK (quantity > 0),
+    price DECIMAL(10,2) NOT NULL CHECK (price >= 0),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (order_id) REFERENCES orders(id),
+    FOREIGN KEY (product_id) REFERENCES products(id)
+);
+
+CREATE INDEX order_items_order_id_idx ON order_items(order_id);
+CREATE INDEX order_items_product_id_idx ON order_items(product_id);
+
+CREATE TABLE payments (
+    id SERIAL PRIMARY KEY,
+    order_id UUID NOT NULL,
+    amount DECIMAL(10,2) NOT NULL CHECK (amount >= 0),
+    payment_method VARCHAR(255) NOT NULL,
+    transaction_id VARCHAR(255),
+    status VARCHAR(20) NOT NULL CHECK (status IN ('PENDING', 'PROCESSING', 'COMPLETED', 'FAILED')),
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
+    FOREIGN KEY (order_id) REFERENCES orders(id)
+);
+
+CREATE INDEX payments_status_idx ON payments(status);
+
+CREATE TABLE product_stats (
+    id BIGSERIAL PRIMARY KEY,
+    product_id INTEGER NOT NULL,
+    orders_count INTEGER NOT NULL DEFAULT 0 CHECK (orders_count >= 0),
+    FOREIGN KEY (product_id) REFERENCES products(id)
+);
+
+CREATE UNIQUE INDEX product_stats_product_id_idx ON product_stats(product_id);
+
+CREATE TABLE audit_logs (
+    id BIGSERIAL PRIMARY KEY,
+    exchange VARCHAR(255) NOT NULL,
+    timestamp INTEGER,
+    data JSONB NOT NULL,
+    CONSTRAINT audit_logs_data_not_empty CHECK (data != 'null'::jsonb)
+);
+
+CREATE INDEX audit_logs_exchange_idx ON audit_logs(exchange);
+CREATE INDEX audit_logs_timestamp_idx ON audit_logs(timestamp);

package.json

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+{
+  "name": "hiring-engineering-code-review-task",
+  "version": "1.0.0",
+  "description": "Code review task in TypeScript",
+  "main": "dist/index.js",
+  "scripts": {
+    "start": "ts-node src/index.ts",
+    "build": "tsc",
+    "test": "jest",
+    "lint": "eslint . --ext .ts",
+    "lint:fix": "eslint . --ext .ts",
+    "format": "prettier --write \"**/*.{ts,tsx,md}\""
+  },
+  "dependencies": {
+    "amqplib": "^0.10.3",
+    "axios": "^1.6.7",
+    "dotenv": "^16.4.1",
+    "express": "^4.18.2",
+    "pg": "^8.11.3",
+    "tsc": "^2.0.4",
+    "uuid": "^9.0.1"
+  },
+  "devDependencies": {
+    "@types/amqplib": "^0.10.4",
+    "@types/express": "^4.17.21",
+    "@types/jest": "^29.5.11",
+    "@types/node": "^20.11.10",
+    "@types/pg": "^8.10.9",
+    "@types/uuid": "^9.0.7",
+    "@typescript-eslint/eslint-plugin": "^6.19.1",
+    "@typescript-eslint/parser": "^6.19.1",
+    "eslint": "^8.57.1",
+    "eslint-config-prettier": "^10.0.1",
+    "eslint-plugin-import": "^2.31.0",
+    "eslint-plugin-prettier": "^5.2.3",
+    "jest": "^29.7.0",
+    "prettier": "^3.4.2",
+    "ts-jest": "^29.1.2",
+    "ts-node": "^10.9.2",
+    "typescript": "~5.3.0"
+  }
+}

src/consumers/orderCreatedConsumer.ts

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+import RabbitMQConnection from "../mq/connection"
+import { AuditService } from "../services/auditService"
+import { query } from "../db"
+import { Order, OrderItem } from "../types"
+
+export class OrderCreatedConsumer {
+  private static readonly QUEUE_NAME = "order_created_queue"
+  private static readonly EXCHANGE_NAME = "orders"
+
+  public static async subscribe(): Promise<void> {
+    const connection = RabbitMQConnection.getInstance()
+    const channel = await connection.getChannel()
+
+    await channel.assertExchange(this.EXCHANGE_NAME, "fanout", {
+      durable: true,
+    })
+
+    const queue = await channel.assertQueue(this.QUEUE_NAME, {
+      durable: true,
+    })
+
+    await channel.bindQueue(queue.queue, this.EXCHANGE_NAME, "")
+
+    channel.consume(queue.queue, async (msg) => {
+      if (!msg) return
+
+      const orderData = JSON.parse(msg.content.toString())
+      await this.processOrder(orderData)
+      channel.ack(msg)
+    })
+  }
+
+  private static async processOrder(orderData: { order: Order; items: OrderItem[] }): Promise<void> {
+    const { order, items } = orderData
+
+    await Promise.all(
+      items.map((item) =>
+        query(
+          `UPDATE product_stats 
+       SET orders_count = orders_count + 1 
+       WHERE product_id = $1`,
+          [item.product_id],
+        ),
+      ),
+    )
+
+    await AuditService.logEvent("order_processed", {
+      order_id: order.id,
+      timestamp: new Date(),
+    })
+  }
+}

src/db/index.ts

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+import { Pool } from "pg"
+import dotenv from "dotenv"
+
+dotenv.config()
+
+const pool = new Pool({
+  connectionString: process.env.DATABASE_URL,
+})
+
+export const query = async (text: string, params?: any[]) => {
+  const client = await pool.connect()
+  try {
+    return await client.query(text, params)
+  } finally {
+    client.release()
+  }
+}
+
+export const getClient = async () => {
+  const client = await pool.connect()
+  return client
+}
+
+export default pool

src/handlers/eventsHandler.ts

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+import { Request, Response } from "express"
+import { AuditService } from "../services/auditService"
+
+export class EventsHandler {
+  public static async index(req: Request, res: Response): Promise<void> {
+    try {
+      const { exchange, limit = 25, offset = 0 } = req.query
+
+      if (typeof exchange !== "string") {
+        res.status(404).json({ error: "Exchange parameter is required" })
+        return
+      }
+
+      const events = await AuditService.getEvents(exchange, Number(limit), Number(offset))
+
+      res.json(events)
+    } catch (error) {
+      res.status(500).json({ error: "Failed to fetch events" })
+    }
+  }
+}