Low‑Level Design Learning Roadmap
Master Low‑Level Design (LLD) step by step. This comprehensive roadmap covers design patterns, object-oriented principles, and implementation strategies essential for building robust software systems.
- Pattern-first approach: Learn when to apply creational, structural, and behavioral patterns, reinforced with modern refactoring techniques.
- Production-grade detail: Every section highlights testing approaches, concurrency concerns, and extensibility considerations you can mention during interviews.
- Bridge the gap: Pair each module with practice problems from the case study library and relevant topics in the HLD roadmap to connect architecture with implementation.
What You'll Master
Study workflow
- Skim the pattern overview, then restate the intent, participants, and consequences without looking at notes.
- Translate the pattern into code in your preferred language, focusing on naming and extensibility.
- Discuss trade-offs with a peer or record a short Loom to practice communicating implementation choices.
Pair each module with a relevant case study to see how the pattern plugs into end-to-end architectures.
Stage overview
Stage 1 • LLD Foundations
Focus: Refresh OOP pillars, SOLID principles, and UML basics.
Categories: LLD Foundations
Practice: Redesign a familiar service (e.g., parking lot) to ensure single responsibility and clear abstractions.
Stage 2 • Creational Patterns
Focus: Construct flexible object creation flows (factory, builder, prototype).
Categories: Design Patterns: Creational
Practice: Implement two variations of the same pattern (e.g., abstract factory vs factory method) and compare extensibility.
Stage 3 • Structural Patterns
Focus: Compose complex objects from simpler ones while keeping coupling low.
Categories: Design Patterns: Structural
Practice: Model facade and decorator patterns for a logging subsystem, documenting pros/cons.
Stage 4 • Behavioral Patterns
Focus: Control interactions between objects, command flows, and state transitions.
Categories: Design Patterns: Behavioral
Practice: Simulate chat notification flows with observer vs mediator and explain trade-offs.
Stage 5 • Production Concerns
Focus: Write clean, testable, thread-safe designs with defensive APIs.
Categories: Code Quality, Concurrency & Threading, API & Error Handling
Practice: Design an end-to-end module (e.g., rate limiter) including concurrency strategy, tests, and error surfaces.
LLD Foundations
Design Patterns: Creational
Design Patterns: Structural
Design Patterns: Behavioral
Code Quality
Concurrency & Threading
API & Error Handling
Ready to Build Better Software?
This roadmap combines time-tested design patterns with modern software engineering practices. Perfect for developers who want to write cleaner, more maintainable code and excel in coding interviews. Each topic includes practical examples, UML diagrams, and real-world implementation scenarios used by experienced software engineers.
Suggested workflow
- Review the concept module and sketch the class diagrams in your own notation.
- Implement a simplified version of the pattern in your preferred language.
- Revisit the pattern in a relevant system design interview scenario to practice storytelling.