In the field of system architecture, where terms like API, MVC, and CDN might initially feel like cryptic jargon, we set out to reveal the sophisticated framework that supports Instagram. This is not merely a casual exploration; creating a system similar to Instagram requires careful planning, much like conducting an orchestra with various instruments, each playing its distinct part. Our methodology will emulate that of an experienced engineer adept at maneuvering through the complex landscape of data and networks.

Picture yourself as a rookie adventurer, eager to gain knowledge but looking as bewildered as a lost kitten. You might dive into a few texts on software architecture only to find yourself confronted with terminology that seems like a secret language crafted by a council of tech sorcerers. You may start questioning if you've stumbled into a different dimension where terms like "scalability" and "load balancing" are commonly used. This blog is designed for newcomers to system design, aimed at guiding you to become a proficient architect of systems, step by step. We will kick off this journey by analyzing the system architecture that underlies Instagram.

Instagram, a giant in social media, provides a platform for users to share their beloved moments through photos and videos. This is a domain dominated by likes, hashtags, and filters. However, our goal is not to disrupt the internet but to foster a clear understanding of system design. In this process, we will create a simplified version of Instagram, envisioning it as the playful younger sibling, eager to emulate its elder but still mastering the basics.

A Brief History

Origins and Early Development (2010): - Established by Kevin Systrom and Mike Krieger in San Francisco. - Initially named Burbn, focusing on location check-ins and photo sharing. - Shifted its focus to mobile photo sharing, rebranding as “Instagram” (a blend of “instant camera” and “telegram”). - Launched on iOS in October 2010, attracting 25,000 users on its first day. - Gained rapid popularity thanks to its user-friendly interface, photo filters, and emphasis on mobile experience.

Growth in Popularity (2011–2012): - Surpassed 1 million users within two months and 10 million within a year. - Released an Android app in April 2012, greatly expanding its user base. - Became a cultural icon, promoting hashtags, influencer marketing, and visual storytelling. - Acquired by Facebook for $1 billion in April 2012, just before Facebook’s IPO.

Global Expansion and Scalability (2013-present): - Launched a web interface in November 2013, followed by dedicated apps for Windows and Fire OS. - Added features like Direct Messages (2013), Stories & Live Video (2016), and Reels (2020). - Grew to over 2 billion monthly active users by 2022, establishing itself as a leading global social media platform. - Encountered challenges related to data privacy, content moderation, and competition from TikTok. - The parent company Facebook rebranded to Meta in 2021, highlighting its focus on metaverse development.

System Architecture

1. Client-Side Application: Instagram primarily functions on mobile devices, featuring native apps for iOS and Android, as well as a web version for browsers. Users interact with Instagram through these applications.
2. Load Balancers: Incoming user requests are managed by load balancers, which distribute traffic evenly across multiple servers. This strategy is essential for maintaining high availability and scalability.
3. Web Servers: These servers handle user authentication, profile rendering, and web content delivery. They use web frameworks and technologies to process user requests and generate dynamic web pages efficiently.
4. API Servers: The API servers offer endpoints for client applications to communicate with the platform. They manage tasks like posting photos, following users, liking posts, and retrieving user data while interfacing with various backend services.
5. Content Delivery: Instagram uses Content Delivery Networks (CDNs) to quickly deliver media content, including images and videos, to users. CDNs cache content at strategically placed edge locations worldwide, significantly reducing latency and improving delivery speed.
6. Databases: A combination of relational and NoSQL databases is employed to manage Instagram's data. Relational databases like MySQL or PostgreSQL handle structured data, while NoSQL databases such as Cassandra or MongoDB manage unstructured data like user-generated content and media.
7. Caching Layer: To enhance system performance and reduce database load, Instagram utilizes caching mechanisms. Frequently accessed data, such as user profiles and recent posts, are cached using technologies like Memcached or Redis.
8. Message Queues: Systems like Apache Kafka or RabbitMQ facilitate asynchronous task management. These queues efficiently handle background tasks, including notifications, email deliveries, and processing user interactions.
9. Search and Discovery: Instagram features a robust search and discovery system powered by search engines like Elasticsearch, enabling users to find accounts, hashtags, and locations with relevant results.
10. Machine Learning: Algorithms play a crucial role in Instagram’s recommendation systems, analyzing user behavior and content to suggest posts, accounts to follow, and ads.
11. Content Moderation: Instagram employs machine learning and image recognition algorithms for content moderation, actively identifying and removing inappropriate or harmful content.
12. Analytics and Reporting: Users and businesses receive analytics and reporting features, with complex algorithms processing user data to provide insights on post reach, engagement rates, and follower demographics.
13. Real-Time Features: Instagram supports real-time features like direct messaging and live video streaming, requiring a robust infrastructure and real-time communication protocols.
14. Security Measures: A range of security protocols, including encryption, authentication, and access controls, are implemented to safeguard user data and ensure platform integrity.

Business Requirements 1. Image Upload: Users should be able to upload images from their mobile devices in various formats and sizes. 2. Likes & Comments: Users need to express their appreciation via likes and engage in discussions through comments on images, with access to view likes and comments. 3. Follow: Users must have the ability to follow other users and receive notifications when they are followed back. 4. News Feed: The system should create a news feed of images, sorted by relevance and freshness.

Technical Requirements 1. The system must support image formats such as JPEG, PNG, and GIF. 2. The maximum image size should not exceed 20MB. 3. It should accommodate at least 100,000 concurrent uploads. 4. Users should be able to upload up to 10 images daily, with a monthly cap of 500 images. 5. The system must manage a minimum of 1 million concurrent likes and comments. 6. To support its vast user base, the system should handle at least 1 billion registered users. 7. Users should be able to follow at least 1,000 others for a rich social experience.

Instagram enforces certain user activity limits to protect the system from misuse and ensure a pleasant experience. While these limits typically do not affect regular users, business accounts and influencers should remain aware of their activities. The limits for individual Instagram users are as follows: - Posts: There is no official daily limit for posting photos or videos. Users can generally post around 20–30 items per day without issues. - Uploads: Up to 10 images or videos per day. - Likes: Maximum of 1,000 likes per day. - Comments: Maximum of 1,000 comments per day. - Follows: Up to 1,000 follows per hour.

Use Cases 1. Upload a New Image:

• When a user uploads an image, the client sends a request with the image data to the Instagram server.
• The server processes the image and stores it in the relevant storage system.
• Metadata, such as captions, locations, and tags, is saved in a database.
• The image becomes accessible to the user’s followers and appears on their profile.

2. Follow Another User:
   • To follow another user, the client sends a request to the server with the target user's ID or username.
   • The server updates the following and follower lists in the database.
   • This relationship data allows Instagram to generate personalized feeds and notifications for both users.
   • New content from followed users appears in the follower's feed.
3. Retrieve User News Feed:
   • When a user requests their news feed, the client communicates with the Instagram server.
   • The server retrieves the list of users the requesting user follows from the database.
   • It fetches recent posts and stories from those users, sorting them by timestamps.
   • The sorted content is sent back to the client for display in the user’s feed.
   • Additionally, algorithms may personalize the feed based on user interactions.

Exceeding these limits may trigger error messages or temporary account restrictions.

Instagram’s Daily Capacity - Maximum uploads per day: 10 - Maximum likes per day: 1 million - Maximum likes per hour: 100,000 - Maximum tags per day: 1,000 - Maximum tags per hour: 100 - Maximum comments per day: 1 million - Maximum comments per hour: 100,000 - Maximum stories per day: Unlimited - Maximum concurrent users: Over 1 billion - Maximum concurrent uploads: 100,000 - Maximum concurrent likes and comments: 1 million

Current Status (2024): - Instagram remains a dominant social media platform, though its growth has decelerated. - The focus is on features like Reels and shopping to compete with TikTok and e-commerce. - Ongoing efforts address data privacy and mental health concerns with new initiatives. - Instagram is integral to Meta’s strategy, but it faces increasing regulatory scrutiny and competition.

Resources: - Instagram Engineering Blog: https://instagram-engineering.com/ (insights into Instagram’s infrastructure) - Facebook Engineering Blog: https://engineering.fb.com/ (articles on related technologies used by Facebook and Instagram)

Real-Time Features: - WebSockets: https://developer.mozilla.org/en-US/docs/Web/API/WebSocket (MDN Web Docs) - Server-Sent Events: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events (MDN Web Docs)

From its modest beginnings in a San Francisco office to its global status as a cultural touchstone, Instagram has transformed how we connect and share experiences. Through a blend of technology and human interaction, it continues to adapt and evolve, facing new challenges while embracing the future of social networking.