Based on Korean Version 1.9.6 (https://hamait.tistory.com/1054), last updated October 2019.

You are not expected to be 100% knowledgeable about those, but instead show your depth in understanding what you have experience with or is interested in. Focus on what you know well.

Part 1: Blockchain

What are Double spending, Replay attack, Eclipse attack

Part 2: Bitcoin

• How can we ensure the integrity of Bitcoin transactions? How do you trust the previous output in the input of the next transaction?
• What’s bloom filter SPV in Bitcoin?

Part 3: Ethereum

• What’s the difference between Transaction and Raw Trasaction?
• What’s nonce in an Ethereum transaction? Why is there no nonce in Bitcoin?

Part 4: Hyperledger fabric

• Explain the transaction flow of Hyperledger fabric
• What is MVCC Collision and Optimistic Lock on Hyperledger Fabric?
• What is MSP in Hyperledger Fabric
• What are channel MSPs and network MSPs in a Hyperledger fabric?
• What’s nonce in Hyperledger fabric. What is the difference with Ethereum’s?
• How events are created in Hyperledger fabric, how can the client know about an event?

Part 5: EOS

Part 6: Hyperledger Indy

Part 7: Consensus

• What are the advantages and disadvantages of the E-O-V consensus process in Hyperledger Fabric?

Part 8: Software

• Tell us about three design patterns you usually use. Write the pseudo-code Implementation of Observer Pattern
• Implement pseudo-code to distribute work among multiple threads and wait for them to finish
• Give me three examples of how to waste space (memory) to improve performance
• What is padding, packing in memory alignment?

Part 9: Java

• Explain Java’s method argument passing method. What’s Shallow Copy / Deep Copy.
• What is the logic error of the following servlet call code (target is exected once after passing through filters)?

//// Filter 
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

        ...  인코딩처리 OR
        ...  로깅처리 OR
        ...  인증처리

        chain.doFilter(request, response);
     
        ...  
}

//// FilterChain

public class FilterChain { 
   private List filters = new ArrayList(); 
   private Target target; 
   
   int currentFilter = 0; 

   public void addFilter(Filter filter){ 
      filters.add(filter); 
   } 

   public Filter getNextFilter(){ 
      if(currentFilter < filters.size()){ 
           return filters.get(currentFilter++); 
      } 
      return null; 
   } 
   public void doFilter(String request, String response){ 
         Filter f = getNextFillter(); 
         if(f != null){  
           f.doFilter(request,response,this);         
         } 
           
         target.execute(request,response); 
   } 

   public void setTarget(Target target){ 
      this.target = target; 
   } 
} 

Part 10: C++

• What’s important about performance degradation and enhancements in C ++
• Parse a single line to collect space-separated words, then code them to print out the word and the number of duplicates. (Performance and memory optimization
• Write a function that takes a string as a parameter and returns a string with certain characters removed. (With performance optimization)
• Briefly describe the auto / override / nullptr / constexpr / atomic keywords in C ++
• Please explain the following code in C ++. (Consumers in the producer-consumer pattern, and there is only one consumer here)

Buffer BufferPool::get_buf(){   
   Buffer* buf = nullptr;
   std::unique_lock<std::mutex> ul(_mtx, std::defer_lock);

   while (buf == nullptr){
    ul.lock();
    if (_pool.empty()) _cond.wait(ul);

    if (!_pool.empty())  // 여기서 pool 이 empty 일 경우는?
    {
       buf = _pool.get();
    }
  }

   .... DO something ....
  return buf;
}

Part 11: Go

• How is the select statement used in Go? Please explain the code below.

package main

import (
   "fmt"
   "time"
)

var scheduler chan string

func consuming (prompt string){
      fmt.Println("consuming 호출됨")
   select {
   case scheduler <- prompt:
      fmt.Println("이름을 입력받았습니다 : ", <- scheduler)
   case <-time.After(5 * time.Second):
      fmt.Println("시간이 지났습니다.")
   }
}

func producing (console chan string) {
   var name string
   fmt.Print("이름:")
   fmt.Scanln(&name)
   console <- name
}
func main() {
   console := make(chan string, 1)
   scheduler = make(chan string, 1)

   go func(){
      consuming(<-console)
   }()

   go producing(console)

   time.Sleep(100 * time.Second)
}

Part 12: Javascript

• What are built-in Javascript objects / browser objects / HTML DOM objects
• What is the difference between ajax and websocket communication
• Show your previous works in React & CSS Styling

Part 13: Distributed systems

• What is consistent hashing?
• What is HAProxy?
• What is Zookeeper and give two examples where you should use it

Part 14: Compilers

• How does EOS charge for resources?
• How to compute CPU, Memory and Storage usage in a program written in C ++ or Go?

Part 15: Cryptography

• What is HMAC / PKI / ECDSA / ECDH
• What is ECert in Hyperledger Fabric? Why does Hyperledger fabric use it?
• How are zero knowledge proofs used in Fabric Identity Mixer?

Part 16: Database

• Compare Red Black tree & B tree & Skip lists data structures.

Part 17: Messaging

Part 18: Networking / Socket

• Tell me as much as you know the difference between socket communication between multithreaded / Select / Java NIO / ePoll / IOCP.

Experience with the following tools

• Agile Management Techniques (* JIRA)
• Product & Configuration Management (Bitbucket)
• Containerization like Docker + Coobernate
• Build Automation (* Bamboo)
• Test Automation (* Unit Test gTest Study)
• Issue Registration Automation (* JIRA)
• Information sharing wiki management (confluence)
• Information sharing chat management (slack)
• Deployment Automation
• Service Management Automation
• Understanding Your Networking Infrastructure
• Understanding Vertical / Horizontal Segmentation
• Understanding and building a non-stop system (extending non-stop resources, etc.)
• AWS Management