Problem Statement

This document describes the core problems that ChatRoom aims to solve.

Real-Time System Challenges

1. Connection State Management

WebSocket connections are stateful, in contrast to stateless REST APIs:

REST API	WebSocket
Stateless	Stateful
Independent requests	Persistent connection
Easy to scale	Scaling requires state migration
Simple load balancing	Requires sticky sessions or message sync

Core Question: How to maintain message consistency across multiple instances?

2. Authentication & Authorization

WebSocket protocol does not support standard HTTP Authorization headers:

Core Question: How to securely authenticate WebSocket connections?

3. Token Security

Problems with traditional single-token approach:

Long-lived Access Token → High leak risk
Short-lived Access Token → Frequent re-login

Core Question: How to balance security and user experience?

4. Message Reliability

Real-time message challenges:

• Ordering: Are messages delivered in order?
• Loss detection: How to detect lost messages?
• Reconnection recovery: How to restore state after disconnect?

5. Horizontal Scaling

Single-instance limitations:

Single WebSocket instance → Limited connections
Multiple instances → How to sync messages?

Core Question: How to implement message sync without introducing Redis?

Design Constraints

Tech Stack Constraints

Constraint	Reason
Go backend	Learning Go language
React frontend	Modern UI development practice
PostgreSQL	Single data source, reduced complexity
No Redis	Keep architecture simple

Teaching Constraints

• Readability first: No over-abstraction
• Progressive complexity: Simple to complex
• Actually usable: Not a toy project

Problem Summary

Problem	Difficulty	Solution
WebSocket Auth	Medium	Ticket approach
Token Security	Medium	Dual Token rotation
Message Sync	High	PostgreSQL NOTIFY
Horizontal Scaling	High	Architecture design

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Next: Solution Overview

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