# Low-Level Design vs High-Level Design Explained When building software systems, design happens at multiple layers. Two of the most important phases are High-Level Design (HLD) and Low-Level Design (LLD). Understanding the difference between them is crucial for developers, architects, and anyone preparing for system design interviews. https://yipyipyo.com/forum/main-forum/74131-casino-i-et-nytt-digitalt-format https://yipyipyo.com/forum/main-forum/75569-making-sense-of-modern-project-collaboration https://yipyipyo.com/forum/main-forum/25091-photosynthesis-lab-report https://yipyipyo.com/forum/main-forum/71825-boltz-stick-retro https://yipyipyo.com/forum/main-forum/53194-can-anyone-advise https://www.fw-follow.com/forum/topic/83615/xoso66wang # What is High-Level Design (HLD)? High-Level Design describes the overall system architecture. It focuses on the big picture — how different components interact with each other. ### **HLD answers questions like:** What are the main system components? How do services communicate? What database will we use? Is the architecture monolithic or microservices-based? How will the system scale? ### Key Elements of HLD System architecture diagram Technology stack selection API contracts Database design (high-level schema) Integration points Example: Designing a ride-sharing system like Uber would involve defining services such as: User Service Driver Service Payment Service Location Tracking Service **At this level, we focus on what components exist and how they interact.** # What is Low-Level Design (LLD)? Low-Level Design focuses on how each component is implemented internally. **LLD answers questions like:** What classes are required? What design patterns will be used? What are the methods and attributes? How will error handling work? How will data structures be organized? LLD is more detailed and closer to actual coding. https://www.fw-follow.com/forum/topic/79988/adaptive-kinetic-mapping https://www.fw-follow.com/forum/topic/81796/sc88-company https://foro.asturmet.com/index.php?topic=64560.0 https://foro.asturmet.com/index.php?topic=64611.0 https://foro.asturmet.com/index.php?topic=64439.0 https://foro.asturmet.com/index.php?topic=1194.0 ### Key Elements of LLD Class diagrams Sequence diagrams Database table structures Method definitions Design patterns implementation **For example, when building the Payment Service:** Define PaymentProcessor class Implement Strategy Pattern for multiple payment methods Create database tables for transactions Handle exceptions and retries This is where developers translate architecture into code-level structure. # When to Use HLD? Use HLD when: Designing large-scale distributed systems Planning infrastructure Choosing databases and frameworks Defining API contracts Discussing scalability HLD is crucial in system design interviews and architectural discussions. # When to Use LLD? Use LLD when: Writing production code Implementing features Refactoring components Applying design patterns Optimizing performance LLD is commonly tested in coding interviews focusing on object-oriented design. # Common Mistakes ❌ Jumping into coding without HLD ❌ Over-engineering LLD too early ❌ Ignoring scalability in HLD ❌ Writing tightly coupled classes in LLD ❌ No documentation for either phase ## Why Both Matter? HLD ensures scalability and maintainability. LLD ensures clean, efficient, and reusable code. Strong engineers understand both perspectives — thinking like an architect while coding like a craftsman. # Final Thoughts High-Level Design and Low-Level Design are not competing concepts — they complement each other. If HLD is the map, LLD is the step-by-step navigation. Master both, and you’ll significantly improve your software engineering skills and system design interview performance.