Let me start by putting one thing forward: System design is not about writing a memorised answer on paper. It’s more about thinking, planning and strategising.
Hence, there is no correct answer, but a correct Framework. Understanding and approaching system design with the RADIO RADIO framework (Requirements, Architecture, Design, Implementation, Optimisation) helps you streamline your answer.
Additionally, you can treat this blog as a framework for everything that requires building a feed, i.e. Twitter, Facebook, or Orkut, for that matter.
But everything beyond that is dependent on your knowledge and understanding of the system.
Designing a platform like Instagram might sound overwhelming at first, but breaking it down using the RADIO framework (Requirements, Architecture, Design, Implementation, Optimisation) makes it manageable and actually kinda fun. I recently took a shot at this, and here's what I came up with, plus a few tweaks and lessons learned along the way.
Requirements
🔧 Functional Requirements:
News Feed that shows text, images, and videos
User info (photo, username) on each post
Like, comment, and share buttons
Pagination or infinite scroll
Lazy loading for media
🚫 Non-Functional Requirements:
Fully responsive (mobile + desktop)
Accessibility compliant
Optimised for performance
Supports A/B testing for features
Localisation and translation support
Bonus points if it supports offline mode and has a fallback UI.
Architecture
Start by defining your core building blocks:
📂 Components:
PostCard
├── TextContent
├── ImageGallery / VideoPlayer
├── UserHeader (avatar + name)
├── PostActions (like/comment/share)
Feed
└── PostCard[]
CommentSection
LikeButton
ShareButton
Each of these is reusable and maintainable — the key to scalable front-end architecture.
Design
Keep your data models clean and normalised. Here's what worked well:
type Post = {
id: string;
text?: string;
images?: string[];
video?: string;
userId: string;
comments: Comment[];
likes: Like[];
createdAt: string;
};
type User = {
id: string;
name: string;
username: string;
avatar: string;
postIds: string[];
};
type Like = {
userId: string;
postId: string;
};
type Comment = {
id: string;
userId: string;
postId: string;
text: string;
createdAt: string;
};
Avoid embedding full User objects inside posts
Use IDs to reference everything
Support multiple images per post (carousel style)
Implementation
Here's how the main flow looks:
Feed Page: loads posts using a custom hook (useFetchPosts)
Loop through PostCard components to render UI
Use libraries like React Query or SWR for cache + fetch
Defer comment loading until user clicks "View all comments"
Suggested folder structure:
/components
/Post
PostCard.tsx
PostMedia.tsx
PostFooter.tsx
/User
/Comment
/hooks
useFetchPosts.ts
/pages
index.tsx // News Feed
Optimization
Performance matters more than ever. Here's what to prioritise:
📸 Lazy load images and videos
🔄 Use IntersectionObserver for infinite scroll
🏔️ PWA support (with service workers)
📑 Bundle splitting + code-splitting
🚀 Skeleton loaders while fetching
🌍 Localised text using react-i18next
📉 Memoise unchanging components with React.memo
TL;DR
Designing Instagram from the front-end isn’t about copying their UI; it's about building a thoughtful system that can scale, perform, and feel native on any device. Use the RADIO framework to break down the chaos into manageable parts, and you'll be surprised how fast it comes together.
