System Design Syllabus (HLD + LLD)

High-Level Design (HLD)

1. Fundamentals

• Serverless vs Serverful Architecture
• Horizontal vs Vertical Scaling
• Threads and Processes
• Pages and Memory Management
• How the Internet Works (DNS, IP, HTTP)
• Client-Server Architecture
• Monolithic vs Microservices Architecture

2. Databases

• SQL vs NoSQL Databases
• In-Memory Databases (Redis, Memcached)
• Data Replication & Migration
• Data Partitioning & Sharding
• Indexing
• Normalization & Denormalization
• Database Scaling (Horizontal & Vertical)
• Database Transactions (ACID Properties)

3. Consistency & Availability

• Data Consistency and Levels
• Isolation Levels
• CAP Theorem
• Eventual Consistency vs Strong Consistency
• Distributed Consensus Protocols (Paxos, Raft)

4. Caching

• What is Cache?
• Cache Types (Application, Database, CDN)
• Caching Strategies (Write-back, Write-through, Write-around)
• Cache Replacement Policies (LRU, LFU, Segmented LRU)
• Content Delivery Network (CDN)
• DNS Caching

5. Networking

• TCP vs UDP
• HTTP (1.0, 1.1, 2.0, 3.0) & HTTPS
• WebSockets & Webhooks
• WebRTC & Video Streaming
• TLS/SSL

6. Load Balancing

• Load Balancing Algorithms (Round Robin, Least Connections, IP Hashing)
• Consistent Hashing
• Proxy & Reverse Proxy
• Rate Limiting
• Circuit Breaker Pattern

7. Message Queues & Event-Driven Architecture

• Asynchronous Processing (Kafka, RabbitMQ)
• Pub-Sub Model
• Message Queues vs Streams
• Event Sourcing & CQRS

8. Microservices Architecture (Deep Dive)

• Why Microservices?
• Service Discovery
• API Gateway
• Single Point of Failure
• Avoiding Cascading Failures
• Containerization (Docker)
• Orchestration (Kubernetes)
• Migrating from Monolith to Microservices

9. Monitoring & Logging

• Logging Events
• Monitoring Metrics
• Distributed Tracing
• Health Checks & Heartbeats
• Anomaly Detection

10. Security

• Authentication Tokens (JWT, OAuth)
• SSO (Single Sign-On)
• Access Control Lists & Role-Based Access Control (RBAC)
• Encryption (At Rest, In Transit)
• Rate Limiting & Throttling
• API Security (OAuth2, OpenID Connect)

11. System Design Tradeoffs

• Push vs Pull Architecture
• Consistency vs Availability
• SQL vs NoSQL Tradeoffs
• Memory vs Latency
• Accuracy vs Latency
• Cost vs Performance
• Failover Strategies (Active-Active, Active-Passive)
• Data Lakes vs Data Warehouses
• Scalability vs Maintainability

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Low-Level Design (LLD)

1. Object-Oriented Programming (OOP)

• OOP Principles (SOLID)
• Class, Object, Interface, Abstract Class
• Composition vs Inheritance
• Dependency Injection

2. Design Patterns

• Creational (Singleton, Factory, Builder)
• Structural (Adapter, Composite, Proxy)
• Behavioral (Observer, Strategy, Command)

3. Concurrency & Thread Safety

• Threads, Synchronization, Locks
• Deadlocks & Starvation
• Thread-safe Collections
• Concurrent Data Structures
• Executor Framework

4. UML Diagrams

• Class Diagram
• Sequence Diagram
• Activity Diagram
• Component Diagram
• Deployment Diagram

5. APIs

• REST vs gRPC vs GraphQL
• API Design Principles
• Pagination, Filtering, Sorting
• Versioning
• Rate Limiting
• API Documentation (Swagger/OpenAPI)

6. Common LLD Problems

• Design a Parking Lot
• Design a BookMyShow System
• Design an Elevator System
• Design a Splitwise System
• Design a File Storage System
• Design a Rate Limiter
• Design a Cache System

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Additional Recommended Topics

• Distributed Transactions (2PC, Sagas)
• Data Modeling (ER Diagrams, Schema Design)
• Bloom Filters & Count-Min Sketch (for Probabilistic Data Structures)
• Idempotency in APIs
• API Gateway Design
• Data Compression & Serialization Formats (Protobuf, Avro)
• Leader Election (ZooKeeper, etcd)
• Quorum & Replication Factor (in Distributed Databases)
• Backpressure Handling in Streams
• Service Mesh (Istio, Linkerd)
• Observability (Logs, Metrics, Traces)
• Chaos Engineering
• Time Series Databases (InfluxDB, Prometheus)