🚀 Caching Proxy Server

A simple Node.js proxy server built with Express that forwards requests to an origin server and caches responses with TTL (Time-To-Live).

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📌 Features

• ✅ Forward requests to any origin server
• ⚡ In-memory caching for faster responses
• ⏱️ TTL-based cache expiration
• 💾 Persistent cache storage (cache.json)
• 🧹 Automatic cleanup of expired cache
• 🎯 CLI-based configuration (port, origin, ttl)
• 🔒 Caches only GET requests (best practice)

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🛠️ Tech Stack

• Node.js
• Express
• Axios
• Yargs
• File System (fs)

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📂 Project Structure

caching-proxy/
│── src/
│   └── index.js
│── cache.json
│── package.json

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⚙️ Installation

git clone <your-repo-url>
cd caching-proxy
npm install

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▶️ Usage

Run the server with:

npm start -- --port 3000 --origin http://dummyjson.com --ttl 60

🔧 Arguments

Argument	Description
--port	Port to run the proxy server
--origin	Base URL of the origin server
--ttl	Cache time (in seconds)

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🔁 How It Works

1. Client sends request to proxy

2. Proxy builds full target URL using origin

3. Cache is checked:

   • ✅ If valid → return cached response
   • ❌ If expired/missing → fetch from origin

4. Response is stored in cache with expiry

5. Cache is saved to cache.json

6. Response is sent back to client

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🧠 Example Flow

First Request

GET /products

• ❌ Cache MISS
• Fetch from origin server
• Store in cache

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Second Request (within TTL)

GET /products

• ✅ Cache HIT
• Instant response

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After TTL expires

GET /products

• ⏰ Cache expired
• Fetch again from origin

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🧹 Cache Cleanup

• Runs automatically every 50 seconds
• Removes expired cache entries
• Updates cache.json

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📡 Example Endpoint

Test route:

GET /home/api

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⚠️ Limitations

• Only caches GET requests
• No cache size limit (can grow large)
• Uses file-based storage (not scalable)

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🚀 Future Improvements

• 🔄 Cache invalidation API (/clear-cache)
• 📦 LRU Cache (size-based eviction)
• ⚡ Redis integration (production-ready)
• 🧾 Cache headers support (ETag, Cache-Control)

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👨‍💻 Author

Khushi Bhardwaj

📄 License

This project is open-source.