Building a Dynamic Profile API in ASP.NET Core for HNGi Stage 0 🐱💻

I just completed Stage 0 of the HNGi13 backend internship, and it was a fantastic exercise in building a dynamic REST API from scratch using ASP.NET Core.

The task was simple on the surface: create a /me endpoint that returns my profile information and a dynamic cat fact fetched from an external API. But it taught me a lot about real-world API practices.

Here’s how I approached it:

1. Setting up the project

• Used Visual Studio to create an ASP.NET Core Web API.
• Added User Secrets locally and mirrored them as Azure Application Settings for deployment.

1. Fetching dynamic data

• Integrated the Cat Facts API (https://catfact.ninja/fact) using HttpClient.
• Added a 5-second timeout and proper error handling, returning 502 Bad Gateway if the external API failed.

1. Structuring the response

• Returned JSON exactly matching the task spec:
  

   {
     "status": "success",
     "user": {
       "email": "...",
       "name": "...",
       "stack": "C#/.NET"
     },
     "timestamp": "2025-10-19T14:00:00.000Z",
     "fact": "Cats sleep 70% of their lives."
   }
  

• Used UTC ISO 8601 timestamps, ensuring every request shows the current time.

1. Deployment

• Deployed on Azure App Service using Visual Studio’s publish profile.
• Added profile secrets in Application Settings for production.
• Tested /me endpoint from multiple networks to confirm it worked reliably.

1. Key takeaways

• Learned how to consume third-party APIs safely with timeouts and error handling.
• Understood the importance of environment-specific configuration (User Secrets vs. production settings).
• Reinforced JSON response consistency and API design best practices.

Outcome

• A fully working /me endpoint that dynamically fetches cat facts.
• Proper error handling and fallback messages in case the Cat Facts API is down.
• Ready for submission to HNGi and demonstrates clean code, proper logging, and deployment skills.