Step 0 Pre-Check: Project Type Detection

Detected Project Type

Primary Type: Full-Stack Distributed Systems & URL Shortening Service (Express 5 + MongoDB / Mongoose + React 19 + Redux Toolkit + TanStack Query & Router) Sub-Category: High-Throughput Redirection Engine, Base62 / Nanoid Cryptographic Slugs, Atomic Analytics Tracking, Layered DAO Architecture.

Evidence

• Backend Core: Express 5.1.0 (backend/package.json), Mongoose 8.1.0, nanoid 5.1.5, jsonwebtoken 9.0.2, bcryptjs 3.0.2, cookie-parser 1.4.7.
• Frontend Core: React 19.1.0, Vite 6.3.5, @reduxjs/toolkit 2.8.1, react-redux 9.2.0, @tanstack/react-query 5.75.5, @tanstack/react-router 1.120.3, Tailwind CSS v4.1.5 (frontend/package.json).
• Architectural Pattern: Enterprise Data Access Object (DAO) pattern (backend/src/dao/short_url.js), decoupled Service layer (backend/src/services/), and custom Express 5 async error handling (backend/src/utils/errorHandler.js).
• Database Schema: Indexed BSON collection shortUrls (backend/src/models/short_url.model.js) with unique compound indexes and atomic $inc click counters.

Documentation Track

• Full Stack / High-Throughput Systems Track: Detailed coverage of URL hashing mathematics, collision probabilities, atomic counter semantics, HTTP 301 vs 302 redirection trade-offs, TanStack server cache invalidation, and horizontal scale-out.