Summary of "System Design Concepts Course and Interview Prep"

This comprehensive tutorial covers essential system design concepts critical for technical interviews and building scalable, reliable, and efficient large-scale distributed systems. The course emphasizes understanding high-level architecture, data handling, networking, databases, APIs, caching, proxies, load balancing, and the trade-offs involved in system design decisions.

Main Ideas and Concepts

1. System Design Fundamentals

System design interviews focus on how to architect systems, not coding.
Importance of understanding the high-level architecture of computers:
- Data units: bits, bytes, kilobytes, megabytes, etc.
- Storage types: HDD (slower, cheaper), SSD (faster, expensive).
- Memory hierarchy: Cache (fastest, smallest), RAM (volatile), Disk storage (non-volatile).
- CPU: Executes compiled machine code.
- Motherboard: Connects all components.

2. Production-Ready System Architecture

CI/CD pipeline (Continuous Integration/Continuous Deployment) automates testing and deployment (tools: Jenkins, GitHub Actions).
Load balancers and reverse proxies (e.g., NGINX) distribute user requests across servers.
External storage servers handle persistent data.
Logging and monitoring (backend: PM2, frontend: Sentry) track system health and errors.
Alerting systems notify developers via Slack or other platforms for quick response.
Debugging involves log analysis, replicating issues in staging, applying hotfixes before permanent solutions.

3. Key Pillars of System Design

Scalability: System growth with user base.
Maintainability: Ease of future improvements.
Efficiency: Optimal resource use.
Design for failure: build resilient systems that maintain functionality during faults.

4. Core System Design Elements

Moving data: Efficient, secure data flow.
Storing data: Choosing appropriate databases, indexing, backups.
Transforming data: Processing raw data into meaningful info.

5. CAP Theorem (Brewer’s Theorem)

Trade-offs between Consistency, Availability, Partition Tolerance.
Only two can be guaranteed simultaneously in distributed systems.
Example: Banking systems prioritize consistency and partition tolerance over availability.

6. System Metrics

Availability: Percentage uptime (e.g., 99.9% = ~8.76 hours downtime/year).
Reliability, Fault Tolerance, Redundancy: Ensure system continues working despite failures.
Throughput: Requests/queries/data processed per second.
Latency: Time to respond to a request.
Trade-offs exist between throughput and latency.

7. Networking Basics

IP addresses (IPv4 and IPv6).
Data packets, IP headers, and Internet Protocol.
Transport layer protocols:
- TCP: Reliable, ordered delivery.
- UDP: Faster, less reliable, used for real-time apps.
DNS translates domain names to IP addresses.
Public vs. private IPs, dynamic vs. static IPs.
Firewalls control network traffic.
Ports identify services (e.g., 80 for HTTP, 22 for SSH).

8. Application Layer Protocols

HTTP: Stateless request-response protocol with methods GET, POST, PUT, PATCH, DELETE.
Status codes: 200 (success), 300 (redirect), 400 (client error), 500 (server error).
WebSockets: Full-duplex communication for real-time updates.
Email protocols: SMTP (sending), IMAP/POP3 (retrieving).
File transfer: FTP.
Secure shell: SSH for secure remote access.
Real-time communication: WebRTC, MQTT (IoT), AMQP (enterprise messaging).
RPC abstracts remote calls as local calls.

9. API Design

CRUD operations (Create, Read, Update, Delete) using RESTful APIs.
REST: stateless, uses HTTP methods, commonly JSON.
GraphQL: flexible queries, avoids over/under fetching.
gRPC: efficient, uses HTTP/2 and protocol buffers, suited for microservices.
Best practices:
- Idempotent GET requests.
- Backward compatibility via versioning.
- Rate limiting to prevent abuse.
- CORS settings to control domain access.

10. Caching and Content Delivery Networks (CDNs)

Caching: Store copies of data for faster access.
- Browser cache (client-side).
- Server cache (in-memory like Redis, or disk).
- Database caching.
Eviction policies: LRU (Least Recently Used), FIFO, LFU (Least Frequently Used).
CDNs: Geographically distributed servers delivering static content closer to users.
- Pull-based CDN: automatically fetches content.
- Push-based CDN: content uploaded