About LLD and HLD: Interview Prep Tips

In this blog , pleas read about the LLD and HLD interview preparation.

About LLD-Low Level Design-

Low Level design speaks about the class diagrams with a specific approach to methods and relations between classes, program specifications and some other low level details of a given system. Low level Design is also called as Object Oriented Design.

The Hiring team while taking interview for LLD, normally assess the candidates for their knowledge on creation of maintainable, flexible and modular reusable software For this they also see how the candidates use principles of Object Oriented design.

When they ask for some design questions, they see how far the candidate understand the idea of creating an elegant, sophisticated object oriented codes which are maintainable also. One has to practice on these as there is no specific standard answers because these are unstructured questions.

The Path for the preparation for the LLD interview:

1.       Deeply study about the Solid and Object Oriented Principles.

2.       Learn all the common design patterns and what are their applications.

3.       Must know the object oriented language. Keep a good command on C++ or Java or C# or Python.

4.       Find out for some open source project(s) and understand the best practices to execute them.

5.       Have a good practice on general question on LLD.

The Interview: In the interview when LLD questions or problems are given, how to solve them

a/ First understand the problem. If you have some queries about it, ask them. Collect all the required details and then start with the basic features of the problem.

b/ Properly define the core classes/objects.

c/ Define or establish a relationship between the classes and objects. Observe the interactions between them.

d/ Define all the methods so that the requisite parameters are fulfilled.

e/ Now apply all the OOD principles and Design patterns to make the system usable and maintainable.

f/ If it is asked that you have to implement a function also, write a well defined and well structured code.

Companies generally look for a candidate who can develop resilient and scalable systems. If some one understand different technologies , his or her demand is high in the market. HLD or high Level Design is also called as System Design. System design shows the complete architecture to be used. It also clearly shows the main items of the design being developed for main product and its interfaces.

How to prepare for HLD interview:

a/ Take some topic of design and prepare to design it. For a better understanding, try to first understand through some videos. These are available on YouTube. Start slowly, understand the things properly and proceed further. Once understood, design it yourself. It will give you a hands-on practice. Use your creativity to give the best design.

b/ Read and understand the basic principles of System Design. This is very important.

c/ Now see the actual examples. This will further strengthen yourself on the basics of design.

d/ Practice on at least 8-10 examples. Take the subject, write the possible solution of your own. Then compare it with the given solution.  It will give you an insight on the subject.

e/ You can do a complete revision of all the points. Do a assessment of yourself, improvise on the weak points.

The interview:

When you face an interview for HLD or System Design, there is a smooth flow from one to other as below :

1/  Complete clarification about functional and non-functional aspects.

2/ Estimates of bandwidth , storage etc.

3/ Data flow.

4/ Design of high level components.

5/ Detailed design.

6/ Then to find out and address the issues which may come up as bottlenecks.

Question may be asked about the components of the system you have chosen in your design. It may also be asked why you chose a particular component and why not some other one? You should have a satisfactory answer for each and every decision you make.