System Design Interview Prep:
A Beginner's Roadmap

Master core concepts, components, and strategies to crack your next interview with confidence.

Introduction

APIs are the glue that holds modern software together. Whether you’re building a web app, mobile service, automation tool, or even just experimenting as a beginner, using the right API can save you time, supercharge your projects, and make your resume stand out. 💥

But with thousands of APIs out there — which ones are actually useful in 2024? This guide cuts through the noise and shows you the best APIs every developer should know about, categorized by what you’re building and why they matter. 🧠

Let’s dive in!

🧭 What is an API, Really?

An API (Application Programming Interface) lets your code interact with another service — like getting weather updates, sending emails, or authenticating users.

Think of it like ordering food at a restaurant:

You (the user) tell the waiter (API) what you want.
The kitchen (server) prepares it.
The waiter (API) brings the response back to you.

It’s how different systems talk — safely and efficiently. 📡🌐 Best Public APIs You Can Use for Free

These are go-to APIs that are beginner-friendly, powerful, and free or have generous free tiers.

1. REST Countries API 🌍

Great for learning API calls or building projects like travel apps or dashboards.

✅ No auth required
📎 restcountries.com

2. OpenWeather API ☁️🌦️

Perfect for weather widgets, location-based projects, or mobile apps.

🆓 Free for basic use
📎 openweathermap.org

3. NewsAPI 📰

Want to show live news headlines in your app?

🚀 Great for learning APIs + building news-based apps
📎 newsapi.org

4. The Cat API / Dog API 🐱🐶

Fun APIs that are perfect for practicing frontend API requests or making playful apps.

📎 thecatapi.com
📎 thedogapi.com

5. GIPHY API 🎉

Add gifs to your chat app, comment box, or fun project.

🔍 Search GIFs, stickers, and trending media
📎 developers.giphy.com

🔐 Authentication & Identity APIs

Secure your app with login, sign-up, and user management — without building it from scratch.

6. Auth0 🛡️

📌 OAuth, Social logins (Google, GitHub), JWT
🧪 Super useful for secure apps
📎 auth0.com

7. Firebase Auth (by Google) 🧩

🔧 Easy integration for mobile/web apps
🔐 Email/password or Google sign-in
📎 firebase.google.com

📦 Backend-as-a-Service APIs

Want to skip setting up your own backend? These APIs offer databases, storage, and hosting out of the box.

8. Firebase (again!) 🔥

💾 Realtime database, hosting, storage
💬 Chat apps, dashboards, user systems
📎 firebase.google.com

9. Supabase 🐘

🛠️ Open-source alternative to Firebase
🧱 Built on PostgreSQL
📎 supabase.io

10. Appwrite 🧰

Self-hosted Firebase-style API suite
👨‍💻 Ideal for privacy-conscious devs
📎 appwrite.io

💳 Payment APIs

Building an e-commerce app or SaaS product? These APIs handle transactions securely.

11. Stripe API 💸

✅ Accept cards, wallets, subscriptions
💻 Amazing documentation
📎 stripe.com

12. Razorpay (India) 🇮🇳

🧾 Easy payment integration for Indian startups
📎 razorpay.com

🗂️ Productivity + Utility APIs

Use these to build helpful tools, automations, or enrich your data.

13. Notion API 📒

Automate task tracking, content creation
Integrate with your portfolio or CMS
📎 developers.notion.com

14. Google Sheets API 📊

Automate data entry, dashboards, and trackers
📎 developers.google.com/sheets

15. GitHub API 💻

Fetch user profiles, contributions, repos
Use for dashboards, resumes, or learning Git data
📎 docs.github.com

🤖 AI + ML APIs

Use the power of artificial intelligence in your own projects.

16. OpenAI API (ChatGPT, DALL·E) 🧠

Generate text, images, code, or chatbot responses
📎 platform.openai.com

17. Hugging Face Inference API 🦙

🤓 Access pre-trained ML models (NLP, vision, audio)
📎 huggingface.co

🌟 Bonus: APIs to Learn from (Even If You Don’t Use Yet)

Twilio API (SMS, WhatsApp integration)
Slack API (build bots or apps in Slack)
Spotify API (show playlists, song info, etc.)

These APIs give you practice with auth tokens, endpoints, pagination, and more — all valuable skills! 💪

🧠 How to Practice Working with APIs

Here are some simple projects:

📍 Weather app using OpenWeather
📰 News dashboard with NewsAPI
📷 GIF search app with Giphy
📊 Portfolio section with GitHub API

Tools to test APIs:

Postman
Thunder Client (VS Code extension)
Browser (for simple GET requests)

📬 Final Thoughts: Your API Journey Starts Here

APIs can seriously level up your projects — and help you stand out as a developer. Whether you’re building for fun, freelancing, or prepping for job interviews, mastering a few key APIs in 2024 will take you far. 🌈

Want more guides like this? Or help implementing APIs into your portfolio? Visit 👉 CodingWithIITians.com for tutorials, mentorship, and job-ready tips.

Happy coding! 💻🚀

FAQs

Q1. What is an API?
An API (Application Programming Interface) is a set of rules that allows different software applications to communicate and exchange data with each other.

Q2. Why are APIs important?
APIs enable integration, automation, faster development, and scalability. They let apps use existing services instead of reinventing the wheel.

Q3. What makes an API “the best”?
A great API should have:

Clear documentation
Ease of use (developer-friendly)
Security & reliability
Good community support
Scalability for different use cases

Q4. What are some examples of widely used APIs?

Google Maps API – for location & navigation
Stripe/PayPal API – for payments
Twitter API – for social media data
OpenAI API – for AI & NLP applications
Firebase API – for authentication, databases, and hosting

Q5. Are all APIs free to use?
Not always. Many APIs offer a free tier with limited requests and paid plans for higher usage. Example: Google Maps offers limited free usage, then charges per request.

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