HLD (High Level Design)

🟢 LEVEL 1 — Foundations

1. Introduction to HLD

• What is High Level Design
• Purpose: bridge requirements to architecture
• Stakeholders: Product, Architects, Leads
• Output: architectural blueprints & decisions
• Timeline in SDLC

2. HLD vs LLD

• HLD scope: system boundaries
• Architecture layers
• Component interactions
• Data flow across systems

🟢 LEVEL 2 — Architecture Components

3. System Architecture

• Frontend architecture
• Backend architecture
• Database architecture
• External integrations

4. Component Identification

• Core components
• Service boundaries
• Module organization
• Layering (presentation, business, data)

🟡 LEVEL 3 — Design Patterns & Principles

5. Architectural Patterns

• Monolithic vs Microservices
• Event-driven architecture
• Layered architecture
• Modular architecture

6. Design Principles

• Separation of concerns
• Single responsibility
• Scalability first
• Maintainability focus

🟡 LEVEL 4 — Data & Integration

7. Data Architecture

• Data flow between systems
• Database selection (SQL vs NoSQL)
• Data consistency requirements
• Caching strategies

8. Integration Design

• API gateways
• Message queues
• Service-to-service communication
• Third-party integrations

🟠 LEVEL 5 — Non-Functional Requirements

9. Performance & Scalability

• Load distribution strategy
• Horizontal vs vertical scaling
• Performance targets
• Bottleneck identification

10. Reliability & Availability

• Redundancy strategies
• Failover mechanisms
• SLA/SLO definition
• Disaster recovery planning

🟠 LEVEL 6 — Security & Governance

11. Security Architecture

• Authentication mechanisms
• Authorization boundaries
• Data encryption at rest & in transit
• Threat modeling

12. Governance & Standards

• Technology choices rationale
• Compliance requirements
• Naming conventions
• Documentation standards

🔵 LEVEL 7 — HLD Documentation

13. Diagrams & Visuals

• System context diagram
• Component diagram
• Architecture diagram
• Data flow diagram

14. HLD Document Structure

• Executive summary
• Architecture overview
• Component details
• Trade-off analysis
• Risk assessment

🔴 LEVEL 8 — Decision Making & Trade-offs

15. Architectural Decisions

• Build vs buy
• Technology selection rationale
• Performance vs cost
• Complexity vs flexibility

16. Trade-off Analysis

• Scalability vs simplicity
• Speed vs maintainability
• Feature richness vs performance

17. Risk Mitigation

• Technical risks in design
• Dependency risks
• Performance risks
• Mitigation strategies

🔴 LEVEL 9 — Review & Validation

18. Design Review

• Stakeholder alignment
• Technical feasibility check
• Requirements coverage validation
• Feedback incorporation

19. Approval & Handoff

• Architecture sign-off
• Transition to LLD
• Team alignment
• Documentation completion