[CS Technical Interview 3] Network That Opens Up Communication

🥲 Getting a developer job, coding tests weren't the end of it.

As a non-major, when I first prepared for a developer job, I was obsessed only with algorithms and coding tests. I gained some confidence and passed most coding tests. However, I kept failing at the next hurdle, technical interviews.
What was the problem? It was the lack of CS (Computer Science) knowledge. In interviews, CS fundamentals were considered much more important than algorithms.

🗣 For actual interviews, 'speaking practice' was important.

Even after filling in my CS fundamentals, interviews were not easy. In an interview at a certain company, I was asked about floating point. It was content I had definitely read multiple times in books and thought I understood, but I couldn't utter a single word. That's when I realized it. Passive learning through simply reading and understanding cannot provide answers in real situations.

To succeed in interviews, you need not only to accumulate a lot of knowledge but also the ability to explain this knowledge. This 'ability to explain' can only be developed through practicing to organize concepts in just a few sentences and articulate them out loud. Through this process, you can also discover what you didn't know precisely. Without sufficient practice, you'll encounter the following problems.

1. Concept Confusion Type

❓Interviewer What are the characteristics of object-oriented programming?
💬 Candidate The SOLID principles. First, S is..(omitted)...

This is a case of confusing similar concepts.
SOLID is an OOP design principle, while the characteristics of object-oriented programming are abstraction, encapsulation, inheritance, and polymorphism.
The moment you mix up related concepts, the interviewer judges that 'your fundamentals are shaky.'
It's not just a simple mistake, but rather it's read as a signal that your conceptual framework isn't solidly established.

2. Lack of Specificity Type

❓Interviewer What are the characteristics of TCP?
💬 Candidate It's a protocol that guarantees reliability.
❓ Interviewer What are the mechanisms that guarantee reliability?
💬 Candidate Uh... well... it makes transmission secure... like that...

This is a case where you only know the What, but lack the How/Why.
You only know the superficial answers and aren't prepared to explain the underlying principles.
TCP establishes communication through connection (3-way handshake), ensures reliability through RDT (sequence numbers, ACK, retransmission, etc.), and maintains quality through flow control and congestion control.
These concepts should be connected as one coherent flow in your mind. Without organizing concepts concretely, you cannot prepare for follow-up questions.

3. Getting tongue-tied with basic questions

❓Interviewer What is HTTP?
💬 Candidate Um... it's for sending and receiving data on the web... something like that...?

It's such a familiar concept, but when asked to explain it in one sentence, the words don't come easily.
Words like request, response, server, and client come to mind, but they don't flow together into a natural sentence.
This is because we've never practiced explaining from definition to principles in one coherent flow.
This isn't a lack of knowledge, but an absence of structure.

Just knowing is not enough. It only becomes true skill when you can express it in words.

🔥 So we created it. The CS Technical Interview Series That Gets You Talking!

🎯 Recommended for these people

Non-majors · Job seekers · Career changers and others who are preparing for technical interviews and need to be able to articulate CS fundamentals verbally

⚡ Lecture Core Kick

💡 Use it like this

💬 Q. The lecture time is short, but will I be able to learn properly?

🖐 Hello! Let me introduce myself! 🙇

I created this course while thinking of my past self, who stayed up all night worrying about fundamentals and had my heart racing over a single interview question.

I started as a non-CS major and understand better than anyone the thirst for fundamentals (CS knowledge, programming languages, etc.). Through self-studying countless materials and building my own know-how, I eventually graduated from Seoul National University and now work as a 🧑🏻‍💻 Kakao developer.

Since childhood, I've been more confident than anyone in combining and reconstructing various materials to create 'my own comprehensive study notes.' This course is precisely that secret notebook born from my 'ultimate self-study know-how' and all my passion and philosophy.

🔥 What makes this course special?

• All of my 'know-how' is included: As a non-CS major, I have fully incorporated my experience and know-how of self-studying CS and programming languages and getting hired at a large corporation. I have included in this course all the methods for how to most efficiently understand complex and abstract concepts and make them your own.

• 'Fundamentals' are key in any development field: Whether you're aiming for game development, AI, web/app development, or any other field, basic knowledge of computer science is not optional but essential. This course helps you become a true expert based on solid fundamentals.

• We compete with 'overwhelming quality': I've referenced countless materials including textbooks, famous university lectures, commercial books, and technical interview resources to extract core keywords and reconstruct them in my own unique way. With intuitive diagrams and illustrations, combined with easy explanations infused with my practical experience, I promise to make even complex concepts click with that "Ah, now I get it!" moment.

🚀 Introducing the third lecture [Network] from the Technical Interview Master Roadmap.

📕 Network, the key to understanding 'invisible connections'!

Networking is a subject that developers must understand at some point, but it often feels like a wall from the very beginning for many people.

• OSI 7 layers, TCP/UDP, NAT, DNS, HTTPS... The terms are familiar, but you can't quite grasp the flow of how everything connects from start to finish❓

• If you're struggling to explain exactly what happens when you enter a URL in a browser during an interview❓

• TCP connections use a 3-way handshake, so why does termination use a 4-way process❓

• Or are you already exhausted from the start because there are too many words to memorize❓

This course is designed for exactly those people, clearly organizing concepts by connecting them based on actual internet communication flow according to the OSI 7-layer structure. Rather than a fragmented listing of concepts, it's structured so you can grasp the context in which concepts appear in the order that data moves between client and server, so there's no more feeling overwhelmed!

🎯 Through this course, you will be able to clearly answer the following questions.

• How does the internet work?
  → Introduces the overall flow through LAN and WAN, data transmission methods, and OSI 7-layer structure.

• What happens when you enter a URL in your browser?
  → Explains DNS, IP, HTTP, TCP/UDP, and port numbers in order.

• What's the difference between TCP and UDP?
  → We'll organize the structural differences through the presence or absence of reliability, flow control, and congestion control.

• Why is NAT necessary?
  → We explain the private IP and public IP structure, NAT operation methods, and practical applications with diagrams.

• How does HTTPS encrypt communication?
  → We'll break down the concepts of symmetric/asymmetric keys and the TLS handshake process in an easy-to-understand way.

• How is network security implemented?
  → Understand the basic protection structure through firewall, SSL/TLS, and encryption elements.

  
  

📌 At the end of the course, a practical interview practice chapter awaits you.

You can now also practice answering core questions that frequently appear in technical interviews, such as "Please explain the difference between TCP and UDP" and "What is DNS?", by training yourself to respond fluently in one or two sentences without hesitation.

📖 A curriculum packed with only the essentials

This is the table of contents and key keywords you will learn in this course.

If there are any unfamiliar keywords, make sure to grasp them thoroughly this time.

✏ Here's what you'll learn

3⃣ Complete mastery of core network concepts frequently encountered in practice

• HTTP/HTTPS, symmetric/asymmetric keys, IP, DNS, TCP and other core network concepts that developers most frequently encounter and need to understand when developing web services and applications are covered in depth.

• Explains how each concept actually works in real communication processes and what roles and importance they have, with practical examples, to strengthen practical capabilities beyond theory.

• Through this, you can solidly build the foundational knowledge needed to identify causes and seek solutions when network-related problems occur.

👀 Course Preview

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💡 Curious about other interview preparation courses? Check out the roadmap below :)

🔗 Technical Interview Master Roadmap

Pre-enrollment Reference Information