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Chain is a computer programming language designed for the development of blockchain applications. It is a fork of the Go programming language, and it was created by Ethereum co-founder Gavin Wood. Chain was first released in 2017, and it is now one of the most popular programming languages for blockchain development. Sources: * [Chain programming language website](https://chain.com/) * [Wikipedia article on Chain](https://en.wikipedia.org/wiki/Chain_(programming_language))

Ask the right questions secure the right Chain talent among an increasingly shrinking pool of talent.

First 20 minutes

General Chain app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Chain application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you explain the concept of blockchain?

Blockchain is a distributed and decentralized ledger that records and verifies transactions across many computers in such a way that the transactions cannot be altered retroactively. It enhances security, transparency, and efficiency.

What are the key features of blockchain technology?

The key features of blockchain technology include decentralization, immutability, security, transparency, and consensus.

Describe the difference between public and private blockchain.

Public blockchains are open to anyone and are secured by cryptoeconomics. Private blockchains, on the other hand, are only open to selected members, and trust comes from the central party.

How would you handle a situation where a blockchain application you developed is not scaling as expected?

I would first identify the bottleneck causing the scaling issue. Then, I would consider solutions such as sharding, off-chain transactions, or implementing a layer 2 solution like Lightning Network or Plasma.

What are smart contracts and how do they work?

Smart contracts are self-executing contracts with the terms of the agreement directly written into code. They automatically execute transactions when predefined conditions are met.

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What you’re looking for early on

Does the candidate demonstrate a strong understanding of blockchain technology?

Is the candidate comfortable with and knowledgeable about relevant programming languages?

Does the candidate show evidence of problem-solving skills?

Has the candidate worked on relevant projects in the past?

Next 20 minutes

Specific Chain development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between proof of work and proof of stake.

Proof of work requires miners to solve a complex mathematical problem to add a new block. Proof of stake, on the other hand, allows validators to create a new block based on the amount of cryptocurrency they hold and are willing to 'stake' for the block validation.

How would you ensure the security of a blockchain application?

I would ensure security by implementing measures such as encryption, secure hash algorithms, digital signatures, and by following best practices for smart contract development to avoid common vulnerabilities.

What are the challenges in blockchain technology?

Some of the challenges include scalability, privacy, integration with existing infrastructure, regulatory uncertainty, and energy consumption.

Describe the difference between a blockchain and a database.

A blockchain is a type of database, but with a specific type of structure and functionality. It is immutable, decentralized, and each block is linked to the previous one, while a traditional database is centralized and can be easily altered.

How would you approach the task of developing a decentralized application?

I would start by defining the problem the application will solve, then design the architecture, including the smart contracts. I would then develop the frontend and backend, ensuring to follow best practices for security. Finally, I would test thoroughly before deployment.

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At this point, a skilled Chain engineer should demonstrate strong problem-solving abilities, proficiency in Chain programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Chain.

What does the following simple JSON object represent?
{ 'name': 'John Doe', 'age': 30, 'city': 'New York' }
This code represents a JSON object with three properties: name, age, and city. The values of these properties are 'John Doe', 30, and 'New York' respectively.
What does the following JSON syntax mean?
{ 'employees': [ { 'firstName':'John', 'lastName':'Doe' }, { 'firstName':'Anna', 'lastName':'Smith' }, { 'firstName':'Peter', 'lastName':'Jones' } ] }
This JSON object contains an array named 'employees'. Each element of the array is an object that represents an employee, with properties 'firstName' and 'lastName'.
What will be the output of the following code snippet that manipulates a JSON array?
var obj = { 'employees': [ 'John', 'Anna', 'Peter' ] }; console.log(obj.employees[1]);
The output of this code will be 'Anna'. It's accessing the second element of the 'employees' array in the 'obj' JSON object.
What does the following code snippet do in terms of threading or concurrency?
var obj = { 'name': 'John Doe', 'age': 30, 'city': 'New York' }; var myJSON = JSON.stringify(obj); localStorage.setItem('testJSON', myJSON);
This code converts a JSON object into a string using JSON.stringify(), and then stores it in local storage. This is a common practice when you want to store data locally in a user's browser in a thread-safe manner.

Wrap-up questions

Final candidate for Chain Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Chain application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the steps involved in a blockchain transaction?

The steps include transaction initiation, block creation, block verification, network consensus, and block addition to the blockchain.

Describe the difference between a hard fork and a soft fork in blockchain.

A hard fork is a change to the blockchain protocol that makes previously invalid blocks or transactions valid, and requires all nodes to upgrade. A soft fork is a change that makes previously valid blocks invalid, and only requires a majority of miners to upgrade.

How would you deal with a situation where a blockchain network is experiencing a 51% attack?

In the event of a 51% attack, the best course of action would be to encourage honest nodes to join the network to dilute the attacker's control. It may also be necessary to implement a hard fork to change the consensus algorithm.

Chain application related

Product Perfect's Chain development capabilities

Beyond hiring for your Chain engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Chain projects, and can engage in multiple capacities.

Chain Consultive assessments

Chain Application Conversion Assessment Chain Application Integration Assessment Chain Data & Database Integration Assessment

Custom Chain development projects

Custom Chain App Conversion Chain Custom App Development Process App UI Design for Chain Facelifts

Hiring guide for Chain Engineers

Chain Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Chain engineer at this point.

Chain Consultive assessments

Custom Chain development projects