Low-level designing is the detailed design of software using components. It is an integral part of any technology company and thus becomes inescapable during the interview. Various questions will be asked of the candidate. The top-low level design interview questions given below will prepare you for a good machine coding round.

Top Low Level Design Interview Questions and Answers for 2024

1. What is Object-Oriented Language?

Object-Oriented Language is required to write coding while designing software. Some widely used languages are C++, Java, Python, and C#. The candidate must know how to write object-oriented code as they could be asked during low-level design interviews.

2. What are object-oriented principles?

Object-oriented principles help to make software maintainable and capable of adapting to changes.

3. Explain some object-oriented principles?

Some well-known principles are

  • DRY

It means don’t repeat yourself. It suggests that a code should not be repeated again and again. If needed, that change has to be done in all other places as well.

  • YAGNI

It means you ain’t gonna need it. It suggests that features should be added only when required to reduce inefficiency.

  • SOLID

It includes single responsibility, open-closed, Liskov substitution, interface segregation, and dependency inversion.

4. What is UML?

UML Stands for unified modeling language. It is not a programming language but a tool used for modeling, visualizing, and creating the software system.

5. Explain the classification of UML diagrams.

There are 14 types of UML diagrams. These are classified into 2 groups:-

Structural Diagrams

Behavioral Diagrams

These include the static view of the system

These include the dynamic view of the system

·       Class diagram

·       Object diagram

·       Component diagram

·       Deployment diagram

·       Profile diagram

·       Package diagram

·       Composite structure diagram

·       Activity diagram

·       State machine diagram

·       Use case Diagram

·       Interaction overview diagram

·       Timing diagram

·       Sequence diagram

·       Communication diagram

6. What are design patterns?

Design patterns are the solutions to some problems that occur during the software designing process. These are tried and tested, hence smoothening the designing process.

7. How can you solve an LLD problem?

There are 3 steps to solve an LLD problem:-

1. Clarifying and gathering requirements

The first step is to understand the problem and gather the requirements And necessary assumptions of the system. Do not assume yourself.

2. Class diagram and use case diagram

Once the requirements are gathered, define the classes and objects and find their relationships. Draw class diagrams, Use case diagrams, and also a schema diagram (if required) to find the data model.

3. Coding

Once the structure is designed, quotes can be written using design patterns, object-oriented, and SOLID principles.

8. What is the single responsibility principle?

It suggests that a class should have a single reason to change. This principle is about each module and its role.

9. What are the advantages of a low-level design?

LLD has various advantages

  • It gives a logical design to a program code
  • It is based on high-level design
  • It forms class diagrams that include
  • Relations between classes and program specifications.
  • It describes the modules for easy coding
  • It develops the software with minimal debugging and testing
  • It includes low-cost and maintenance

10. What is the difference between a sequence diagram and an activity diagram?

  • A sequence diagram represents the objects to visualize the flow of the design, but an activity diagram represents all the cases and flows in a single diagram.
  • A Sequence diagram gives the overview of the whole system, whereas an activity diagram Gives a holistic picture of the system.
  • In the case of a movie booking system, the sequence diagram includes a booking controller, a booking manager, and a payment processor. But, an activity diagram includes the detailed process, from the display of a list of movies and theaters to the reservation of seats.

11. Which is the most popular design pattern used?

The most frequently used design patterns are Singleton, Factory, and Strategy. They don’t require memorizing the code.

12. How will you create a good traffic light system?

While creating an effective traffic light system, these points need to be considered

  • Firstly I will find out the amount of vehicle and pedestrian traffic in the target area.
  • I will also check the flow of traffic and pedestrian crossing time for the length of each light cycle.
  • To program the timer, I need to understand the time taken by vehicles to clear the intersection before the light changes.
  • During programming, traffic signals need to be put along with the timer (20-30 seconds between signal changes).
  • Traffic lights should be installed at such places where it is visible to all the motorists and pedestrians.

13. What is multithreading?

Multithreading is the process of breaking a code into independent tasks or threads to use resources efficiently. When the 2 tasks are independent of each other, they can be launched parallel to each other, thus achieving multi-threading.

14. Explain the process of designing software?

The software designing process includes

  • Identifying the business problem
  • Gathering requirements
  • Defining high-level components
  • Designing the components in a detailed manner
  • Writing the code
  • Testing the software
  • Releasing of the software
  • Maintenance of the software

15. List all the design patterns.

Creational Patterns

Structural Patterns

Behavioral Patterns

·       Builder pattern

·       Factory pattern

·       Singleton pattern 

·       Composite pattern

·       Decorator pattern

·       Facade pattern

·       Observer pattern

·       Strategy pattern

·       Visitor pattern

16. What does the Singleton Design pattern mean?

This creational pattern means that only one object of a particular class should be created and provides its global access.

17. What does Strategy Pattern mean?

It means that a class behavior or its algorithm can be changed at run time.

18. What are good coding practices?

  • Well-structured codes must be used.
  • Codes must adhere to quality standards.
  • Complex codes should be avoided to reduce errors. Simple and readable codes must be used.
  • Focus on solving a problem naturally instead of fitting design patterns into the code forcefully.

19. Explain the advantages of using SOLID Principles.

SOLID Principles are certain standards to be followed by software developers. They have various advantages

  • They help in identifying faults that lead to bad software designs.
  • They help developers to handle complex designs.
  • They make the code logical and readable.
  • They help the developers to change software without altering the other.

20. What is the code review?

It is a process of reviewing each other’s codes to identify mistakes, improve code quality, and accelerate the process of software development. It is also called Peer Code Review.

21. What are the advantages and disadvantages of design patterns?

Design patterns are the tried and tested solutions that save resources during software development and make the process simple. Developers do not have to solve a problem again and again as they have prior design patterns.

These design patterns require extensive knowledge. Also, established patterns hinder the scope of creativity and the zeal to find new and better solutions.

FAQs

1. What can I expect at a Low-Level Design interview?

Knowledge of low-level design is an integral part of any IT job. LLD gives an insight into how to design software. During an interview, Several technical questions related to LLD will be asked. This round is also sometimes called machine coding or pair programming round. So it is better to understand the concepts of LLD and not get confused with high-level design questions.

2. Can we use Python for LLD?

Low-level designing needs coding that is written in an object-oriented language. Python is one of the object-oriented languages widely used by coders.

3. What is LLD System Design?

Low-level design is a step-by-step process used to design data structures, software, source codes, and performance algorithms.

LLD designs a High-level design system into ready-to-code components.

4. Why is Low-Level Design important?

Softwares is the heart of any IT company. LLD is required for building software. There lies the importance of LLD

  • LLD builds software data capable of adapting to change over time
  • It takes into account all the requirements and components necessary for building a software
  • It enables smooth implementation and testing
  • It also ensures the maintenance of the software

The low-level design interview round can be a little tricky. Here are a few tips for smoothly clearing this round-

  • Understand the interviewer’s question thoroughly. Do not try to make self assumptions.
  • List all the requirements of the design before proceeding further.
  • Do not rush and take your time while designing.
  • Discuss your problems and answers with the interviewer.
  • Practice the common questions beforehand.
  • Be confident and try to give yourself 100%.

Conclusion

Hope this article was able to help you prepare better for the low-level design interview. With these low-level design interview questions and answers, you will be able to answer the interviews with confidence and better preparedness. If you are looking to enhance your skills further, we would recommend you check Simplilearn’s Post Graduate Program in Full Stack Web Development. This program is designed in collaboration with Caltech CTME and can help you hone the relevant skills and become job-ready.

If you have any questions or doubts, feel free to post them in the comments section below. Our team will review them and get back to you with the solutions at the earliest.

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