title: Low-level design (LLD) description: Object-oriented design for SDE2 interviews: Python fundamentals, design patterns and machine-coding problems with tested packages.
Low-level design (LLD)¶
Low-level design rounds test whether you can turn requirements into clean, extensible, working classes - often while coding live. This section covers the Python and design fundamentals interviewers expect, the patterns worth naming and the machine-coding problems that come up most often, each with a tested package. Start with the LLD interview framework, learn the P0 patterns, then solve the P0 problems against the clock.
Sections¶
- Fundamentals - 8 pages: Python, SOLID, UML, concurrency and the LLD framework
- Design patterns - 32 pages: the patterns worth naming, with tested Python and the classic confusions
- Problems - 36 pages: machine-coding problems with complete tested packages
Start here (P0)¶
Fundamentals¶
- Object-oriented Python for interviews
- SOLID in Python
- UML with Mermaid
- The LLD interview framework
- Concurrency for LLD in Python
Design patterns¶
- Design patterns overview
- Singleton
- Factory Method
- Builder
- Adapter
- Decorator
- Facade
- Command
- Observer
- State
- Strategy
- Template Method
- Repository
- Dependency Injection