As a software engineer at Amazon London, I’ve learned the value of mastering CS fundamentals for a successful career in tech. From my own experiences and constant learning, I can confidently attest that delving into these core areas is the key to unlocking doors to top-tier companies as an SDE.

While creating this list and I tested myself too and luckily performed well 😄 so don’t be scared of, the list is concise yet covers everything you need to know. It’ll surely help you excel and open up exciting job opportunities. So, embrace these essential concepts, and you’ll thank me later for this valuable advice.

List contains topics for each subjects below:

Operating Systems

Process Management:

• Process States and Transitions
• Process Scheduling Algorithms (e.g., FCFS, SJF, Round Robin, etc.)
• Interprocess Communication (IPC) mechanisms (e.g., pipes, shared memory, message queues)
• Threads and Thread Synchronisation (mutex, semaphore, condition variable)
• Deadlock Detection and Prevention

Memory Management:

• Virtual Memory and Paging
• Page Replacement Algorithms (e.g., LRU, FIFO)
• Segmentation and Paging Combined
• Memory Allocation Strategies (e.g., Best Fit, Worst Fit, First Fit)

File Systems:

• File System Structure and Components
• File Operations (e.g., create, read, write, delete, update)
• Directory Implementation (e.g., single-level, two-level, hierarchical)
• File Allocation Methods (e.g., contiguous, linked, indexed)

CPU Scheduling:

• Scheduling Algorithms (e.g., Priority Scheduling, Multi-level Queue Scheduling)
• CPU Burst Time and Turnaround Time Calculation
• Context Switching and Preemption

Database Management Systems (DBMS):

Relational Database Concepts:

• Entity-Relationship Model (ER Model)
• Relational Algebra and SQL queries
• Relational Integrity Constraints (Primary Key, Foreign Key, Unique Key)

Normalization:

• 1NF, 2NF, 3NF, BCNF, and their implications
• Functional Dependency and Decomposition

Transaction Management:

• ACID Properties (Atomicity, Consistency, Isolation, Durability)
• Transaction States (Active, Partially Committed, Committed, Aborted)
• Concurrency Control (e.g., Locking, Two-phase locking)

Indexing and Query Optimization:

• Index Structures (e.g., B-trees, Hash Indexes)
• Query Execution Plans and Cost Estimation
• Query Optimisation Techniques (e.g., Join Strategies, Index Selection)

Networking:

OSI Model:

• Understand the seven layers of the OSI model and the functionality of each layer.
• Know the data encapsulation and decapsulation process at each layer.

TCP/IP Protocol Suite:

• Familiarize yourself with the TCP/IP protocol stack and its key protocols such as TCP, UDP, IP, ICMP, ARP, and DNS.

IP Addressing and Subnetting:

• Learn about IPv4 and IPv6 addressing, including IP classes, CIDR notation, and subnet masks.
• Practice subnetting to divide IP address spaces into smaller subnets.

Routing and Switching:

• Understand the basics of routing and switching in computer networks.
• Learn about routing protocols such as RIP, OSPF, BGP, and EIGRP.
• Explore switching techniques like VLANs and Spanning Tree Protocol (STP).

Network Devices and Technologies:

• Know the functionality and use cases of various network devices such as routers, switches, hubs, and firewalls.
• Understand network technologies like NAT (Network Address Translation) and VPN (Virtual Private Network).

Network Security:

• Study common network security mechanisms, including firewalls, intrusion detection and prevention systems (IDS/IPS), and access control lists (ACLs).
• Learn about encryption protocols like SSL/TLS and IPsec.

OOPs

Classes and Objects:

• Instance Variables
• Instance Methods
• Constructors
• Instance Variables vs. Class Variables: Understand the difference between variables that belong to instances (objects) and those that belong to the class itself.

Abstraction:

• Abstract Classes
• Interfaces

Encapsulation:

• Access Modifiers: Public, private, protected, and package-private (default) access modifiers that control the visibility of class members.
• Getters and Setters

Inheritance:

• Single Inheritance
• Multiple Inheritance
• Method Overriding

Polymorphism

• Compile-time (Static) Polymorphism:
• Method Overloading: Defining multiple methods with the same name but different parameter lists.
• Operator Overloading: Defining custom behaviors for operators when used with objects.
• Runtime (Dynamic) Polymorphism:
• Method Overriding: Subclasses provide a specific implementation of a method defined in their superclass.

SOLID Principles:

• Single Responsibility Principle (SRP)
• Open/Closed Principle (OCP)
• Liskov Substitution Principle (LSP)
• Interface Segregation Principle (ISP)
• Dependency Inversion Principle (DIP)

If you aim to join top companies as an SDE, these topics are a must-know. Happy Coding 🎉

Hey Guys! I hope you are doing well.

My self Nitesh Yadav and currently living in Delhi, India. Glad to share that I got an offer from Amazon, London as Software Engineer (CTC = 1CR+ INR) and would like to share my whole journey.

Educational Background:

I was an average student during my schooling. But my plan was clear at that time that I want to become a software engineer, and just focused to crack IITs (as everyone’s dream). I worked very hard and did self-preparation which was not enough. In the end, couldn’t make it to IITs or NITs. Even not able to qualify for the JEE MAIN exam.

I had a backup at that time which was IP University to get Btech CSE and got a seat in one of the reputed colleges of IP University. But, because of poor financial conditions couldn’t able to pay the joining fee.

I don’t want to stop or want to take a drop. So, I decided to go with BSc. Computer Science from the University of Delhi. I hope you all are thinking about why I didn’t prepare for the next 1 year for IITs or some good college. In short, why not dropped for 1 year for preparation. Because I have seen the struggle of my parents to feed and give good education to us (me and 2 younger sisters) and want to support my family asap.

I didn’t get much exposure during my graduation as we were the first BSc. CS batch for that college. Theoretically, I became very strong when it comes to CS fundamentals and DSA. Also, started a little bit practicing coding problems on Hackerrank. When I got to know that there are no on-campus placements and friend’s cousins are a good place after MSc. So, I just started preparing for MSc. from DU.

After securing Rank 2 in the entrance exam of DU MSc. CS, I entered here. I would say that this is one of the best decisions. I got good exposure and a lot of guidance (kind of roadmap to crack good companies) from seniors.

Beginning of Preparation (#struggle)

After the 1st semester, I started working on my problems solving skills from Leetcode and explored multiple platforms. Worked hard af* and before on-campus placement, around 400 problems were solved on Leetcode in 1 year.

I am not a hardcore competitive programmer. I mean, I tried to be for 4–5 months then realized that this is not my cup of tea. So, I stopped competitive programming and focused on DSA and development.

Now, You guys are thinking that this much preparation is enough to crack any FAANG companies. But, during on-campus placements, I got to know that only hard work is not going to work, you need a pinch of luck too. Don’t know what’s wrong was happening but I was not able to clear online test rounds of most of the on-campus companies.

I was only able to clear an online round of 3 companies out of 15–20. One of them is Amazon for the intern role. I reached the final round of Amazon but couldn’t make it. That is a huge hit for me that after doing so much preparation I wasn’t able to clear. Finally, got selected by a service-based company that I joined in Jan 2021.

After taking a break for a couple of months, I collected the things that went wrong and started my preparation again with more intensity. Parallelly was applying for multiple companies and filled around 250–300 application forms of product-based companies. Nothing went well in the whole of 2021. I was not getting any calls or responses from companies even after getting referrals too. The only thing that is in my favor is that I was leading a project in my organization and the learning curve is so high.

It’s never easy to stick with the preparation plan as I was not getting any interview calls. But I never stopped my preparation and thought that getting off-campus is too difficult. So, I have to be fully ready if the single opportunity comes to me I am going to crack that.

Now, 2022 started, and got an interview call from Browerstack at the end of Jan. After the 6 rounds (2 months process), I got selected and received an offer of a 100% hike. I was really happy that finally, I made it.

In between the interviews with Browerstack, I also got a call from Swiggy and again after 5–6 rounds, I got selected with a decent offer. I resigned from my current service-based company as have to serve 3 months notice period.

As of now, since the last 2–2.5 years, I referred to these platforms and solved the following number of problems.

• Leetcode (600)
• GeeksforGeeks (250+)
• InterviewBit (150+)
• Binary Search (200+)
• Hackerrank (150+)
• HackerEarth (100+)
• CodeChef (100+)

Then, I got the opportunity in Amazon (AWS) from a recruiter on LinkedIn while I was serving the notice period. He told me that my LinkedIn profile looks good and if I am interested then have to share my resume.

I would say this maybe my luck which gives me the International opportunity from Amazon and my consistency hardwork grabbed it with both hands.

Amazon Interview Experience

The whole interview process follows a typical Amazon interview pattern that contains DSA and leadership questions not any system design questions in my case.

• Online Test
• Phone Screening test
• Round 1 (Technical)
• Round 2 (Technical)
• Round 3 (Managerial )
  No DSA problems. This was totally based on behavioral questions.
• Round 4 (Managerial or Bar-raiser)

All the interviews were for 1 hour and the time slot is well defined.

1 hour interview:
- 5mins (intro)
- 20mins (leadership questions)
- 30mins (DSA problems)
- 5 mins (Q & A)

All the interviewers were super friendly and made me comfortable at the beginning of the interview.

I can’t disclose the exact problems because of NDA. But the coding problems were of easy-medium difficulty level and questions belong to BFS, Hashmap, DP, Arrays, and Trees.

They have asked a lot of behavioral questions which need to reflect their leadership principles. Behavioral questions are as much important as DSA. So, one must prepare well these questions if going for interviews at Amazon. I have used STAR techniques to give answers to all behavioral questions.

Few links to prepare DSA/behavioral questions for Amazon:

• Leadership principles
• STAR Method
• Data Structure and Algorithms
• Interview Preparation Guide

After around 2 months of the interview process, I got one of the biggest good news, that I have cracked Amazon (AWS) London and received an offer of 1CR+ INR.

Preparation Tips

• Do not blindly follow others’ roadmap. Because that worked for them and may or may not work for you. So, adjust accordingly and make your own planned roadmap/schedule.
• Do not waste much time on a single problem. I have seen this as a very common issue. I’ll tell you, how I handle this thing?
  First of all, I have decided particular time slot on the basis of the difficulty level of the problem.
  Easy problems: 10–15 mins
  Medium problems: 20–25 mins
  Hard problems: 40–45 mins
  after, spending decided time if I wasn’t able to solve the problem then just see the solution and attempt it again the next day (remember not on the same day).
  Make sure you are fully focused while solving a particular problem.
  This technique helped me a lot and I was able to attempt at least 4–5 problems per day without wasting time.
• Stuck with a single platform but it’s better if you are exploring multiple coding platforms and then decided which one suits you.
• Do not compare yourself to others (most important). Do not forget that everyone has some X-factor.
• Do not make an infeasible schedule like solving 5 problems a day for 6 months. Always take a break for a couple of days after long practice weeks.
• Enjoy life!

End Notes

Myths about international offers that I have broken are:

• You must have to be from IIT/NITs or top tier-1 college. I was not belonging to top colleges.
• You need Btech. or Mtech. degree. I have degree of MSc. CS although it doesn’t matter if you have skills.
• You must have experience in a product-based company. My company was a service-based company when I switched.
• You must have a good amount of experience around 3–4 years. I have 1 YOE.
• You must be a pro competitive programmer. I am not.

I would say this happened because I believed in myself and my preparation. So, don’t reject yourself. Have faith!

Thank you so much for reading. I tried my best to put every aspect here and hope it motivates you guys.

Keep working on your dream. If I can do it, everyone can do it.

Follow me for any kind of help on LinkedIn and Twitter.