Chapter_34

🚀 Chapter 34: Deploying FastAPI App on Vercel

This chapter shows how to publish your FastAPI application live using Vercel (serverless Python support). You’ll learn how to connect your GitHub repo, configure Vercel, and deploy your FastAPI project.

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🎯 Why Vercel?

• Offers serverless functions for Python / FastAPI. :contentReference[oaicite:0]{index=0}
• Automatically builds on each commit (CI/CD) when linked to GitHub. :contentReference[oaicite:1]{index=1}
• Easy to configure via a vercel.json. :contentReference[oaicite:2]{index=2}

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📋 Prerequisites

• A GitHub account
• A Vercel account (free plan is sufficient)
• Your FastAPI application in a GitHub repository
• requirements.txt listing all Python dependencies
• vercel.json configuration file (explained below)

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1️⃣ Prepare Your FastAPI Project

1. Ensure your project has a requirements.txt (run pip freeze > requirements.txt)
2. Create a vercel.json file in the root of your project. Example configuration:

{
  "builds": [
    {
      "src": "main.py",
      "use": "@vercel/python"
    }
  ],
  "routes": [
    {
      "src": "/(.*)",
      "dest": "main.py"
    }
  ]
}

• "src": "main.py" refers to your FastAPI entry file.
• The routes section ensures all requests route to main.py.
• You may need to adjust paths if your file structure is different. ([DEV Community][1])

3. (Optional) Specify Python version via pyproject.toml or Pipfile. ([Vercel][2])

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2️⃣ Push to GitHub

1. Initialize git (if not already):

   git init
   git add .
   git commit -m "Initial FastAPI commit"

2. Create a GitHub repository and push:

   git remote add origin https://github.com/yourusername/yourrepo.git
   git push -u origin main

3. Ensure your repository is public or that Vercel has access if private. Vercel supports deployment from GitHub directly. ([Stack Overflow][3])

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3️⃣ Connect to Vercel & Deploy

1. Go to vercel.com → Log in

2. On Vercel dashboard → New Project → Import Git Repository

3. Authorize Vercel to access your GitHub account

4. Select your FastAPI repo

5. Vercel should detect it's a Python project.

6. In Project Settings → Environment Variables → add any secrets (e.g. MONGO_URI, tokens).

7. Click Deploy

8. Wait for deployment to finish — your FastAPI API is live!

   • Use https://your-project.vercel.app as base URL
   • Your API endpoints (e.g. /docs) should work

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4️⃣ Using Vercel CLI (Optional)

If you prefer local control:

npm install -g vercel
vercel login
vercel link  # link your local folder to Vercel project
vercel --prod  # deploy to production

This allows you to deploy without pushing to Git every time. ([Vercel][4])

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5️⃣ Troubleshooting Tips

Issue	Solution
404 on your API endpoints	Check your vercel.json routing config. ([Vercel Community][5])
“Unable to find any supported Python versions”	Ensure your requirements.txt exists and the vercel.json build config is correct. ([Stack Overflow][6])
Private repo not listed	Grant Vercel access in GitHub settings or make the repo public. ([Stack Overflow][3])

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✅ Final Checklist

• requirements.txt present
• vercel.json configured
• GitHub repo pushed
• Vercel project created & linked
• Environment variables set
• Deployed and tested endpoints

Once done, your FastAPI app is live and accessible globally via Vercel’s infrastructure. Congratulations — you’ve deployed your API!