30+ Ethereum Interview Questions And Answer


Are you looking for Ethereum interview questions? If you do, then you are not alone. There is a huge surge in demand for Ethereum developers. As a blockchain learner, you should not give up the opportunity to advance your career.

In this article, we will go through the top Ethereum interview questions. You will also find many Solidity interview questions, as they both are related to each other.

Why Ethereum? Understanding its demand

Ethereum has been the most popular decentralized ledger technology out there. It is partially because of the Ethereum cryptocurrency, and the ability to create decentralized apps through the Ethereum blockchain solution.

Ethereum is a public blockchain solution. There is also an enterprise implementation of Ethereum, which enables companies to implement a permissioned Ethereum network.

The ecosystem of Ethereum makes it a great choice for developers. It has one of the most deployed decentralized apps on blockchain networks. Its ease of use and the ability to use Solidity to program smart contracts and dApps opens up a lot of opportunities for the organizations out there.

There is no doubt that 2020 is the year where blockchain is in high demand. This also makes one of the top technologies for which companies are seeking talent.


Preparing for Blockchain Interview

Before we go and list the top Ethereum blockchain interview questions, it is important to learn how to prepare for an interview, especially for a blockchain interview. The good news is that we already have covered the topic, and you can check it here: How To Prepare For A Blockchain Interview.

You should also check out Top 50 Blockchain Interview Questions And Answers 2019 as it will help you in answering more generic blockchain-related questions in the Ethereum interview.

We also encourage you to check out Blockchain Specialist and Blockchain Architect as it will help you to understand what companies are currently looking for.

If you are a total novice, then you should check out the 101 Blockchains Academy, where you can get both beginners and advanced blockchain-related courses.

30+ Ethereum Interview Questions And Answers

Let’s get started with the Ethereum developer interview questions.

Q: What is the Ethereum network? Explain in short

A: Ethereum is a second-generation distributed ledger technology that builds upon the bitcoin network. It was first launched in 2015, and it has continued to grow from there. It is an open-source public distributed ledger technology. Technically, it is also an operating system with key features such as smart contracts, transaction-based state transitions, and virtual machines. 

Q: Who is the founder of Ethereum?

A: There are two original authors of Ethereum, including Vitalik Buterin and Gavin Wood.

Q: What is EVM?

A: EVM stands for Ethereum Virtual Machine. It is a decentralized virtual machine capable of handling scripts using the public nodes network. It is also Turing complete and utilizes Gas as an internal pricing mechanism. 

Q: What are the real-world use-cases of Ethereum?

A: There are many use-cases of Ethereum. Some of them are as below.

  • Decentralized Finance: One of the biggest use-cases is decentralized finance(De-Fi). It improves how the financial sector works and improves loans using smart contracts. 
  • Digital Identity: Digital Identity is another use-case where a person’s identity is digitized, providing better usability for individuals as they do not have to carry documents and can be verified instantly through a connected network.
  • Health applications: Healthcare systems can utilize Etereum based solutions to implement a decentralized network and improve things such as drug tracking, better patient management, and so on.
  • Tokenization: Ethereum is very useful in creating the tokenization of real-world assets. This makes it easy to trade items on the blockchain.
  • Payments: It also improves payments, especially cross-boundary transactions.

Q: Tell us about the Enterprise Ethereum Alliance(EEA)?

A: The Enterprise Ethereum Alliance(EEA) was created in March 2017 by Fortune 500 companies, research groups, and blockchain startups. It has more than 100+ non-profit organizations as members. The focus is to create a member-driven standard that can develop an open blockchain specification for interoperability and harmonization. It also facilitates a permissioned implementation of the Ethereum network fine-tuned according to the enterprise requirements. 

Q: What is the value token for Ethereum?

A: The token value of Ethereum is Ether(ETH).

Read more here: How Contract Management Solutions And Blockchain Work Together

Q: What is the Ethereum node?

A: Ethereum nodes talk with each other using the Ethereum protocol. They interact with the outside world using the JSON-RPC interface.

Q: What is Ether?

A: Ether is best defined as a crypto-fuel(token) that powers the Ethereum network. It powers the smart contracts and provides the nodes an incentive to validate the Ethereum blockchain blocks. Once a block is validated, 5 Ether is released to nodes that took participation in the process.

Q: What is Wei? How does it differ from Ether?

A: Wei is the smallest unit in the Ether cryptocurrency that is used in the Ethereum network.

1 Ether = 1018 Wei. It is important to break down Ether as it can help nodes to maintain the amount of Ether required for certain actions. It also helps the cryptocurrency market as people can buy or sell a fraction of Ether.

Q: What is Blockchain?

Blockchain is a distributed ledger technology where peers are capable of communicating and transacting without the need for a centralized authority. The concept of blockchain was invented with the release of Bitcoin paper in 2009. To manage the Network independently without the need for a centralized authority, consensus algorithms are used. Bitcoin used the Proof-of-Work(PoW) consensus algorithm. Right now, blockchain is evolving at a rapid pace with new ways to manage distributed ledger technologies.

Read more about Blockcahin here:

Q: What is the consensus algorithm?

A: Consensus algorithm is best defined as the way to validate transactions in a distributed ledger technology. It is a way to reach agreement or consensus among peers about the state of the DLT. This method is very important as without it, the core philosophy of the distributed ledgers would not stand. There are many popular consensus algorithms out there, including Proof-of-Work(PoW), Practical Byzantine Fault Tolerance(PBFT), Proof-of-Stake(PoS), Proof-of-Burn(PoB), and so on.

Q: Explain how Proof-of-Work(PoW) works?

A: Proof-of-Work is a consensus algorithm that requires work from miners to validate the transactions. The work is generated by solving complex computational problems using hardware. It is not environmentally friendly as it requires a lot of electricity to run the hardware, which in turn solves those complex computational problems.

Q: Which consensus algorithm does Ethereum use?

A: Right now, Ethereum utilizes Proof-of-Work as its consensus algorithm. Ethereum network is in the process of changing its consensus algorithm to a more environmentally friendly consensus method Proof-of-Stake(PoS).

Q: What is the difference between Bitcoin and Ethereum blockchain?

A: The main difference between Bitcoin and Ethereum blockchain is how they work and their features. Bitcoin is a first-generation blockchain technology that offers the foundation of the decentralized ledger. Ethereum, on the other hand, builds on what Bitcoin has to offer by providing a more scalable and programmable blockchain solution. Ethereum supports smart contracts and the ability to design and implement distributed apps(dApps).

Q: What are smart contracts?

A: Smart contracts are like legal documents in code. It is a computer protocol that can be used as a digital verification process or enforce negotiations between parties. Smart contracts are also transparent and automated. In short, it offers a conflict-free approach to deals, agreements, and disputes.

Q: What are the main steps of Smart Contract development from a business perspective?

A: Many key steps are required to be taken when doing smart contract development. The steps are as below.

  • Reconfirm that your business really needs smart contract development.
  • Understand the limitations of smart contracts
  • Plan how to carry out the development
  • Hire a smart contract developer
  • Do proper testing before deploying the smart contract

Q: What is dApps?

A: dApps stands for decentralized applications. These applications are created to take advantage of blockchain technologies. dApps offer many benefits including being decentralized and open source. It also follows protocols and incentivizes nodes that take part in the functioning of the dApp.

Ethereum is a popular blockchain network for dApps as it offers the right ecosystem for developers to create real-world dApps. Other blockchain networks that support dApp creation include TRON and EOS.

Q: Where are the transactions recorded?

A: The transactions are recorded in a public ledger in the case of Ethereum. However, if a permissioned network is used, then the records are stored in a private ledger with certain information available to the public. 

Q: What is the programming language used to write smart contracts and dApps?

A: Solidity is the main programming language that is used to create both dApps and smart contracts. However, smart contracts in Ethereum can also be written using any of the smart-contract languages(SCL). Some of the SCL examples include Vyper, Bamboo, Serpent, Ethereum bytecode, Pyramid, L4, and others.

Q: What is Truffle?

A: Truffle is a popular testing and development environment for Ethereum. It also offers an asset pipeline, which makes it handle Ethereum based projects. With it, a developer can create smart contracts, dApps, do automated testing, configure and build pipelines and so on. It is a perfect framework for developers using Ethereum.

Q: What is block time and average block size in Ethereum?

A: The block time is 2 KB, whereas the average block size is 14 seconds.

Q: Tell us about the type of Ethereum networks that exist.

A: There are three types:

  • Private Network
  • Test Network, e.g., Rinkeby and Ropsten
  • Live Network, i.e., the main Network

Q: Can a transaction be kept hidden?

A: In the case of the public Ethereum network, no transactions can be kept hidden. All transactions are public.

Q: What are the benefits of having a private network?

A: Private networks are very useful when it comes to data privacy. It is also useful for permissions testing and control.

Q: What are the private keys?

A: Private keys are used to secure an address. It should be kept secure by the owner as anyone who has it gives the ownership to the one who possesses it. In contrast, the public key is available online.

Q: How to mine Ethers?

A: To mine ethers, one needs to have a wallet and tools such as Geth CLI. With it, you need to participate in the Network and help add transactions to the blocks.

Q: Is the user’s private key used to sign transactions?

A: Yes.

Q: How do you recover an Ethereum account with no private key?

A: It can only be recovered in only one way: 12 work mnemonic which was set during the account creation process.

Q: What is Geth?

A: Geth is a command-line interface used when running a full Ethereum node.

Q: How can you connect to a node?

A: You can connect to a node using three ways: WS-RPC, JSON-RPC, and IPC-RPC.

Q: What is Geth’s fast sync?

A: Geth’s fast sync works with syncing the download transaction 

Q: What is the functionality of testnet?

A: Testnet is used to connect to the Ropsten Network.

Q: Tell us about Smart Contract use cases?

A: There are many use-cases for smart contracts. For instance, it can be used in real estate where a seller can set up a smart contract to sell properly. The property can be transferred to the buyer once he transfers the property amount.

Q: What is MetaMask?

A: MetaMask is a popular browser-based Ethereum wallet that can be used to interact with the dApps on the Ethereum network. 

Q: Do you need to use real Ether to test dApps and smart contracts?

A: No, it is not required. In test networks, you can use free Ether.

Q: How does spending work in smart contracts?

A: If there is a request that does not modify the smart contract and is used to return values, then there is no cost associated with the task. However, any action that can be used to modify the smart contract test will cost money, i.e., Gas.

Q: What is Remix?

A: Remix is a useful online tool that can be used to deploy, test and develop smart contracts. By using it, developers can quickly test their smart contracts.

Q: How Bitcoin and Ethereum differ when it comes to checking the latest state.

A: Ethereum checks the latest state for the account balance. Bitcoin, on the other hand, checks unspent transaction outputs(UTXO).

Q: What happens when the Gas runs out without the transaction being complete?

A: In this case, all the state changes are reversed. The used Gas is given to the miner.


This leads us to the end of our best Ethereum Interview questions. Ethereum is huge and hence requires careful study. If you are seriously planning to crack the Ethereum interview, then you should have a good in-depth knowledge of it. Simply relying on the interview questions won’t take you far.

So, what do you think about the Ethereum job interview questions and answers? Comment below and let us know.

About Author

Nitish holds a BSc in computer engineering. He is a blockchain enthusiast and in spare time likes to read about the moon. His articles have published on Dzone, InfoWorld, and Hongkiat.

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