LLD stands for low-level design and the goal here is to code different components of a system. Specifically, the idea here is to design classes, their members and the interaction among them. The prime focus while doing this is to take care of following principles -

1. Correctness
2. Readability
3. Extensibility

1. Inheritance
2. Polymorphism
   2.1 Compile-time (Function Overloading)
   2.2 Runtime or dynamic (Function Overriding)
   
3. Encapsulation
4. Abstraction
5. Association, Aggregation and Composition

1. Class diagram (Structural UML)
2. Sequence, usecase, activity diagrams (Behavioral UML)

1. https://en.wikipedia.org/wiki/SOLID
2. https://www.youtube.com/watch?v=HoA6aZPR5K0
3. https://www.freecodecamp.org/news/solid-principles-explained-in-plain-english/
4. Separation of concerns - https://en.wikipedia.org/wiki/Separation_of_concerns (Microservices as an example)

https://en.wikipedia.org/wiki/Software_design_pattern

Types

1. Creational - Singleton, Factory, Prototype, Builder
2. Structural - Facade, Adaptor, Decorator, Proxy
3. Behavioural - Observer, Strategy, Iterator, Chain of responsibility

Which design pattern to pick?

1. Design logger
2. Design slf4j
3. Design a rate-limiter
4. Design a cache
5. Design publisher subscriber
6. Design producer consumer
7. Design a tic-tac-toe https://www.youtube.com/watch?v=gktZsX9Z8Kw
8. Design a parking lot
9. Design an elevator https://github.com/eMahtab/design-an-elevator-system
10. Design a chess game

1. Spring Boot Component, Service, Repository, Controller
2. Refactoring by Martin Fowler https://github.com/HugoMatilla/Refactoring-Summary
3. Facade, Adaptor, Decorator, Proxy