How To Prepare for Programming and Coding Interviews? Topics and Skills

There is no doubt cracking the Coding interviews of top tech companies like Google, Microsoft, and Amazon is very hard, but you can still crack it by carefully planning and preparing the essential skills which matter most like Data structures and Algorithms, System Design, Multithreading and Concurrency, SQL and Database design, and of course, problem-solving skills.

Being an author of Java and a programming blog, I often receive queries about how to prepare for coding interviews? How to pass Google or Microsoft Software Developer interviews? Or how can I get a software development job on Amazon or Facebook?

After answering many of my readers one by one on Facebook and LinkedIn, I thought to put together a list of essential topics for coding interviews.

This list will give a good head-start for your preparation for any tech company interview like Google and Amazon. However, even if you are not targeting Google and just want a Software developer job, you can still prepare these topics.

In fact, preparing for tech giants like Google, Amazon, Apple, and Facebook means you are miles ahead of other candidates, and you will most likely secure many job offers from smaller firms, startups, and investment banks.

That's why I suggest aiming higher because even if you don't get what you want, you will still get job offers that are desirable by many programmers.

Another critical thing to note is that different interviews need different skills. For example, when you go for a Java developer interview, you are bound to know Java. Similarly, for a Python developer interview, it's expected you to know Python and some popular Python frameworks like Django and Flask.

For a Web developer, HTML, CSS, and JavaScript are core skills, and you will be grilled on those, apart from modern web development frameworks like Angular, React, and Vue.js, with a bit of node.js as well.

I'll not touch that topic but I'll share essential skills that are required to pass all of those interviews. They are also known as core programming skills, and it's expected from every software developer to know that.

How To Prepare for Coding and Programming Interviews

Anyway, without wasting any more of your time, here is my list of topics you can prepare to boost your chances on Google, Amazon, and Microsoft programming job Interviews.

1. System Design

This is another crucial topic you need to prepare well for your programming job interviews, especially at big tech companies like Google, Microsoft, Amazon, and Facebook. You need to have some ideas about how to design your solution from architecture to coding.

System design is actually very vast. At a high level, it covers things like software architecture, I mean the advantage between monolithic and microservice architecture and choosing between a NoSQL and SQL database.

Does it cover things like how we will design an application that can handle 10000 concurrent users? And includes things like scalability.

At a low level, it covers Object-Oriented Programming and Design, which talk about designing your classes and their relationships, following good coding practices, and software design principles like SOLID.

Because of this, many candidates struggle to answer system design questions, and if you want to succeed, you must put particular emphasis on this skill. If you need a resource, I recommend you to check the System Design Interview courses, which are prepared by people who served as hiring managers on those tech companies and walk you through common system design interview questions.

For Object-Oriented design and analysis, I recommend the Head First Object-Oriented design book to learn fundamentals and practice.

2. Data Structure

As a programmer, it's Ok if you cannot write web apps using Django or React, but it's Not Ok if you don't know how a hash table works and when to use a list over an array? And, what advantages B-Tree offer over an array? Data Structure and Algorithms are the core of computer science and programming, and it's expected for every software developer to have a solid knowledge of fundamental data structure.

It's imperative to have a good understanding of data structure for writing a robust, performant application that your users will appreciate.

Imagine, if Facebook or Google takes 1 minute to log you in, you will never go there, forget how important they are. Performance is critical, and unless you understand how your program is working and how your data is stored, you will not go anywhere.

In technical interviews, you will be asked to optimize your solution for time and space. You can't do that unless you have a solid understanding of how your code works and how data is stored and accessed.

This is probably the most important topic for coding interviews and you should prepare it well. At a bare minimum, you should know about the array, linked list, binary trees, binary search tree, self-balanced trees like AVL tree, hash table(or map or dictionaries as known in Java and Python) stack, queue, and graph.

You should understand how to store and access elements from these data structures and the computing cost involved. You should also have a comparative analysis of when to use a particular data structure like for a faster search array, and the hash table is better. Still, for faster addition and deletion, a linked list will outperform an array.

If you need a resource to get up to speed, I suggest you pick a data structure course where examples are shown in the language you are most comfortable with. 

3. Algorithms

While it's important to know the essential data structure like an array, linked list, and trees, it's equally important to learn how to work with those data structures. If you don't know the difference between linear search and binary search algorithms, and what it means to run in O(log n) as opposed to O(n^2), you need to spend some time learning algorithms.

This can often be the difference between a fine-tuned application and a slow, crappy process that hangs more than it works. At a bare minimum, you should know about sorting algorithms like quicksort, mergesort, heapsort, etc. searching algorithms like binary search, and some graph algorithms like fastest route-finding algorithms, which are the base of many deliveries and taxi-hailing apps like Uber, Grab, and Ola.

You should also understand how the library methods you are using for sorting an array work, which algorithm it uses internally, and when a different algorithm would do a better job.

I strongly suggest you prepare for this topic in depth. If you need a resource, I would recommend the Grokking Algorithms book by Aditya Bhargava and Algorithms course on Coursera.

4. Multithreading and Concurrency

Concurrency is one of the most desired skills by employers, and also one of the most advanced topics brought up in interviews. Because it shows your ability to design a program that efficiently uses resources but at the same time it's a very tricky topic to master and that's why interviewers love it.

Concurrency can also be used to gauge your expertise and technical depth and is often used as a key deciding factor in your overall hiring level. Whether you are just entering your career or are looking to switch jobs, it never hurts to dedicate some time to mastering concurrency.

At a bare minimum, you should know about threads, processes, shared memory, monitors, locks, critical section, and deferred callbacks. Having a good knowledge of how to avoid race conditions and deadlock can be even better.

Practicing classical concurrency interview questions like Producer-Consumer, Dining Philosopher, and others can also teach you a lot about concurrency and multithreading and give you the confidence to visualize how code and data work when multiple threads run in parallel.

If you have an interviewing coming up, then I highly suggest you double down on concurrency. This is because I know it can be one of the most challenging topics brought up during most of the interviews, even for experienced developers. However, gaining a mastering concurrency will put you at a considerable advantage over other candidates.

5. SQL and Database Design

As a software developer, working with a relational database is a critical skill that you'll need, and it will stick with you no matter where you are in your career.

Every company from small to large uses a DBMS, so it's likely that you will come across different data models, type so databases (NoSQL and SQL), and dependencies on various companies.

Knowing how to structure your data within a DBMS is critical. Should you use an entity-relationship (ER), model? A hierarchical model? A three-schema architecture?

The choices can be intimidating, but it's good to know about the different ways to structure your data so that when you switch database vendors like from Oracle to SQL Server or PostgreSQL, you can plugin with minimal hand-coding.

As a programmer, you should also know about SQL, not just the syntax but also how the database actually runs your query and how joins are executed, how to index are used, and the difference between table scan, index scan, and index seek. These details are not just important from the coding interview perspective but also from day-to-day jobs.

I suggest you go through with Database Design Fundamentals for Software Engineers courses, where you will learn about the different concepts and techniques you can use to structure your data and explore why you should use particular approaches for certain problems.

You will also be exposed to techniques like normalization, which help to increase the efficiency o the database and avoid duplication. I also suggest Use The Index Luke book to better understand how SQL query works in general.

6. AWS, Docker, and Kubernetes

While these five are definitely must-have skills for coding interviews, employers are nowadays also looking for modern tech skills like AWS, Docker, and Kubernetes, which makes them important topics for technical interviews.

Since cloud computing is the next big thing and this decade of software development will be cloud-native, it's better for a software developer to know about Cloud and modern deployment tools like Docker and Kubernetes.

This is also important if you want to stay ahead of the curve and give a reason to your employer to hire you than the next candidate in line. For AWS and Cloud, one more thing you can do is to get a certification, not because you can't get a job without certification but to learn better and get recognition for your skill.

Docker is a container, which allows you to run your application as a whole, along with all the dependencies. This makes both development and deployment easier, particularly for Microservices. Since the container makes cloud deployment more manageable, they are also easier for the manager to scale up and down.

Kubernetes is a container orchestration tool, which means it can use manager containers at scale. It's easy to deploy and manage a few boxes, but when you have to deploy 100s of containers for your application for a promotion event like Amazon prime Sale and then need to take it down once traffic returns to normalcy is not easy. Kubernetes can do that for you and provide automation and peace of mind.

While both Docker and Kubernetes are not mandatory skills for a programmer but definitely essential from the Job perspective. I recommend every Software developer or aspiring programmer to learn Docker and Kubernetes.

That's all about some of the most important skills and topics you can prepare to crack the coding interview of companies like Google, Microsoft, Apple, Facebook, and Amazon. 

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