Slack Flow

A real-time messaging backend inspired by Slack, built with Node.js, Express, Socket.io, MongoDB, BullMQ and Redis. This project demonstrates core backend concepts including WebSocket authentication, real-time communication, background job processing, and clean architecture patterns.

Note: This is a feature implementation showcasing key backend concepts, not a full Slack clone.

Features

Authentication & Authorization

• JWT-based authentication for REST APIs
• Socket.io connection authentication via JWT handshake
• Role-based access control (Admin/Member) for workspaces

Real-Time Messaging (Socket.io)

• Channel Messages — Send and receive messages in workspace channels
• Direct Messages — Private 1:1 conversations between users
• Typing Indicators — Real-time typing status for channels and DMs
• Auto-Join Rooms — Users automatically join all their channels/DM rooms on connection (Slack-like behavior)

Workspace Management

• Create workspaces with unique join codes
• Add members with role assignment
• Create channels within workspaces
• Workspace-scoped messaging

Background Job Processing (BullMQ + Redis)

• Asynchronous email delivery via job queue
• Retry mechanism with exponential backoff (3 attempts)
• Job monitoring via Bull Board dashboard (/admin/queues)

API Design

• RESTful API with versioning (/api/v1)
• Request validation using Zod schemas
• Centralized error handling with custom error classes
• Correlation ID tracking for request tracing

---

Tech Stack

Category	Technology
Runtime	Node.js with TypeScript
Framework	Express 5
Database	MongoDB (Mongoose ODM)
Real-time	Socket.io
Queue	BullMQ + Redis
Auth	JWT + bcrypt
Validation	Zod
Logging	Winston (daily rotate files)

---

Architecture

src/
├── config/          # Environment & service configurations
├── controllers/     # Request handlers (REST + Socket)
├── middlewares/     # Auth, error handling, correlation ID
├── models/          # Mongoose schemas
├── repositories/    # Database access layer
├── services/        # Business logic
├── validators/      # Zod schemas for validation
├── producers/       # Job queue producers
├── workers/         # Background job processors
├── queues/          # Queue definitions
├── routes/          # API route definitions
└── utils/           # Helpers, constants, custom errors

---

How It Works

Socket Connection Flow

Client connects with JWT token
         │
         ▼
┌─────────────────────────────────┐
│  Socket Auth Middleware         │
│  - Validates JWT                │
│  - Attaches user to socket      │
└─────────────────────────────────┘
         │
         ▼
┌─────────────────────────────────┐
│  Auto-Join Rooms                │
│  - Fetches user's workspaces    │
│  - Joins all channel rooms      │
│  - Joins all DM conversation    │
│    rooms                        │
└─────────────────────────────────┘
         │
         ▼
  User receives messages from
  ALL their channels & DMs

Message Flow

User A sends message
         │
         ▼
┌─────────────────────────────────┐
│  Validate with Zod              │
│  Save to MongoDB                │
│  Broadcast to Socket.io room    │
└─────────────────────────────────┘
         │
         ▼
  All users in channel/DM
  receive the message instantly

Email Queue Flow

Action triggers email (e.g., workspace invite)
         │
         ▼
┌─────────────────────────────────┐
│  Producer adds job to queue     │
│  (with retry config)            │
└─────────────────────────────────┘
         │
         ▼
┌─────────────────────────────────┐
│  Worker picks up job            │
│  Sends email via Nodemailer     │
│  Retries on failure (3x)        │
└─────────────────────────────────┘

---

API Endpoints

Authentication

Method	Endpoint	Description
POST	/api/v1/users/signup	Register new user
POST	/api/v1/users/signin	Login and get JWT

Workspaces

Method	Endpoint	Description
POST	/api/v1/workspaces	Create workspace
GET	/api/v1/workspaces	Get user's workspaces
GET	/api/v1/workspaces/:id	Get workspace details
PUT	/api/v1/workspaces/:id	Update workspace
DELETE	/api/v1/workspaces/:id	Delete workspace
GET	/api/v1/workspaces/join/:code	Get workspace by join code
POST	/api/v1/workspaces/:id/members	Add member
POST	/api/v1/workspaces/:id/channels	Add channel

Channels & Messages

Method	Endpoint	Description
GET	/api/v1/channels/:id	Get channel details
GET	/api/v1/messages/:channelId	Get paginated messages

---

Socket Events

Client → Server

Event	Payload	Description
NewMessage	{ body, channelId, workspaceId }	Send channel message
NewDirectMessage	{ body, receiverId, workspaceId }	Send DM
Typing	{ channelId?, recipientId?, isTyping }	Typing indicator

Server → Client

Event	Description
NewMessage	New channel message received
NewDirectMessage	New DM received
Typing	Someone is typing

---

Setup

Prerequisites

• Node.js 18+
• MongoDB
• Redis

Installation

# Install dependencies
npm install

# Create .env file
cp .env.example .env

# Start development server
npm run dev

Environment Variables

PORT=3001
NODE_ENV=development
JWT_SECRET=your-secret-key
JWT_EXPIRY=1d
DEV_DB_URL=mongodb://localhost:27017/slack-flow-dev
REDIS_HOST=localhost
REDIS_PORT=6379
MAIL_ID=your-email@gmail.com
MAIL_PASSWORD=your-app-password

---

Client Usage Example

import { io } from "socket.io-client";

// Connect with authentication
const socket = io("http://localhost:3001", {
  auth: { token: "your-jwt-token" },
});

// Listen for messages (from ALL channels/DMs - auto-joined)
socket.on("NewMessage", (message) => {
  console.log("Channel message:", message);
});

socket.on("NewDirectMessage", (message) => {
  console.log("DM received:", message);
});

// Send a channel message
socket.emit(
  "NewMessage",
  {
    body: "Hello team!",
    channelId: "channel-id",
    workspaceId: "workspace-id",
  },
  (response) => {
    console.log("Sent:", response);
  }
);

// Send a direct message
socket.emit("NewDirectMessage", {
  body: "Hey!",
  receiverId: "user-id",
  workspaceId: "workspace-id",
});

// Typing indicator
socket.emit("Typing", { channelId: "channel-id", isTyping: true });

---

License

MIT