??What is System Design?

?? Ever wondered how Instagram loads millions of images instantly? Or how Uber finds the nearest driver in seconds? That’s the power of System Design!

?? Introduction to System Design

System design is the process of architecting and structuring software systems to handle real-world use cases while ensuring scalability, reliability, and efficiency. It’s not just about coding—it’s about making critical design decisions regarding architecture, components, data flow, and trade-offs.

?? Why is System Design Important?

? Scalability – Ensures your system can handle millions of users (like Netflix, Instagram, Uber).

? Performance Optimization – Reduces response time, increases throughput.

? Reliability & Fault Tolerance – Keeps the system running even when failures occur.

? Maintainability & Extensibility – Makes it easy to add new features without breaking existing ones.

?? Imagine if Facebook’s chat system slowed down every time a new user joined—bad design = bad user experience!

?? Types of System Design

1?? High-Level System Design – Defines major components, their interactions, and architecture (e.g., monolith vs. microservices).

2?? Low-Level Design (LLD) – Focuses on detailed implementation, database schema, class diagrams, and APIs.

?? Example:

?? High-Level Design: A ride-booking system (like Uber) would include services like:

• User Management
• Ride Matching
• Payment Processing
• Notifications

?? Low-Level Design:

• How does ride-matching work?
• Which data structures should we use to find the nearest drivers efficiently?

?? Core Components of System Design

Every large-scale system is built on key components:

1?? Clients & Servers

• Client: Browser, mobile app → Sends requests.
• Server: Processes requests, returns responses.
• Example: Instagram's backend processes millions of photo uploads per second.

2?? Database (SQL & NoSQL)

• Stores and retrieves structured/unstructured data.
• Examples: MySQL, PostgreSQL (SQL), MongoDB, DynamoDB (NoSQL).
• Example: Amazon uses DynamoDB to handle millions of shopping transactions.

3?? Caching (For Speed)

• Stores frequently accessed data to reduce database load.
• Examples: Redis, Memcached.
• Example: Netflix caches popular movie thumbnails for faster loading.

4?? Load Balancer (For Scaling)

• Distributes traffic across multiple servers to prevent overload.
• Examples: NGINX, HAProxy, AWS ELB.
• Example: Twitter uses load balancers to manage heavy traffic spikes.

5?? Message Queues (For Async Processing)

• Handles background tasks like notifications, logging, etc.
• Examples: Kafka, RabbitMQ, SQS.
• Example: LinkedIn uses Kafka to manage millions of real-time notifications.

6?? CDN (Content Delivery Network)

• Serves cached content from nearby servers to improve speed.
• Examples: Cloudflare, Akamai, AWS CloudFront.
• Example: YouTube uses CDNs to stream videos faster worldwide.

?? Key System Design Considerations

Every design decision involves trade-offs:

?? Real-World Example: How Does WhatsApp Work?

WhatsApp processes millions of messages per second with:

1?? Clients (Mobile Apps) → Send messages.

2?? Load Balancer → Distributes requests across multiple servers.

3?? Message Queue (Kafka) → Temporarily stores messages.

4?? Database (NoSQL like Cassandra) → Stores chat history.

5?? Push Notification Service → Alerts users of new messages.

?? Challenge: Ensuring messages never get lost while keeping the system fast. ?? Solution: WhatsApp uses replication, caching, and distributed queues for speed & reliability.

?? Next Steps: Hands-on Activity!

Scenario: Design a URL Shortener like Bit.ly

?? Consider these:

?? How would you store URLs efficiently?

?? How do you ensure unique short URLs?

?? What database would you use and why?

?? Comment below with your approach! Let’s discuss and learn together. ??

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