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Top 30 Interview Questions for Ethereum & Smart Contracts

Top 30 Interview Questions for Ethereum & Smart ContractsAre you planning to prepare yourself for Ethereum interviews and become a successful Ethereum Expert? You have landed on the right page. This article talks about the top Ehereum and Smart Contract interview questions so that you can mentally prepare answers for them.

Table of Contents 

  • Top Ethereum and Smart Contract Questions You Should be Prepared for 
  • Concluding Lines

Top Ethereum and Smart Contract Questions You Should be Prepared for 

1 ) What is Ethereum?

Ethereum is an open software platform based on blockchain that runs on a network rather than running on a single computer. It offers Ethereum developers and experts a decentralized trust-less platform to build and deploy decentralized applications that run on the Ethereum blockchain and whose execution is monitored by thousands of peers.

 2) What is that primary function that powers applications and programs built on Ethereum?

Smart Contracts

3)  What are Smart Contracts?

Smart Contracts can be defined as digital agreements that execute automatically based on real-world input data. They are computer program code capable of facilitating, executing, and enforcing the performance of an agreement utilizing Blockchain technology. 

4)  Explain Ether

Ether is Ethereum’s native cryptocurrency, which is arguably the second most popular digital token after bitcoin (BTC).
Ether can also be termed as a significant fuel for operating the distributed application platform Ethereum.

5 ) How Ethereum differs from Bitcoin?

Bitcoin was created with the aim of providing an alternative to national currencies. In contrast, Ethereum was introduced as an open platform to promote immutable, programmatic contracts and applications via its very own currency, Eth. Where Bitcoin transactions take minutes, Ethereum transactions are executed in seconds. Also, Bitcoin is just a cryptocurrency, whereas Ethereum is also a ledger technology that organizations are utilizing for building new programs and decentralized applications. And out of both the technologies, Ethereum is far more robust.

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6) How Ethereum differs from Ripple?

Taking about Ripple, the main aim of Ripple is to allow real-time global payments globally without the usual friction of exchange rates. On the other hand, Ethereum aims at broadening the use of blockchain technology using smart contracts. It enables smart contracts and decentralized applications to be built and run without any downtime, fraud, or interference from a third party. 

Ripple uses a mechanism called Federated Byzantine Agreement (FBA), which works differently to Proof-of-State(PoS), that Ethereum uses as a consensus mechanism.

7) What is EVM?

Ethereum Virtual Machine(EVM) is a decentralized virtual machine handling scripts using the public nodes network.  EVM is operated in a sandboxed environment which is isolated from the main network. It is assumed to be a perfect testing environment.

8)  What is the average block size and block time in Ethereum?

Block size in Ethereum is around 30-50 kb and the block time is approximately 10-15 seconds. 

9) What is Blockchain technology?

Blockchain is a chain of blocks(data) stored on multiple computers (servers) distributed over a vast geographical region. It is a distributed ledger that maintains a copy of all digital assets.

It is said to be a decentralized distributed ledger tracking of one or more digital assets on a peer-to-peer network(P2P).

10) What is a node in Ethereum? How can you connect with a node? 

A node is a computer connected to the network, which is responsible for processing transactions. You can connect to a node by WS-RPC, JSON-RPC, and IPC-RPC.

11 ) Can you “hide” a transaction? Where are transactions stored?

No. It is impossible to hide a transaction, and all transactions are visible to everyone. Transactions are stored in a public ledger.

12) What is the role of the consensus algorithm? Ethereum uses which consensus?

A blockchain’s consensus mechanism ensures that there is agreement among various parties on the current state of the blockchain and determines who can add new blocks of transactions. Further, it ensures that the chain is not re-written.

Ethereum has switched from Proof-of-Work(PoW) to Proof-of-State(PoS) consensus mechanism.

13) How to obtain Ethers?

Ethers can be obtained by mining or by trading Ethers with other cryptocurrencies. 

14) What are dApps?

Decentralized applications (dApps) are digital applications that exist and run on a peer to peer(P2P) network of computers instead of a single computer. 

15) Which programming language is used to write smart contracts and dApps?

Solidity is the primary programming language used for writing smart contracts and dApps. 

16) What is Truffle?

Truffle is an open-source framework for rapid dApp development and smart contract life cycle management. It is considered to be a perfect framework for developers using Ethereum.

17) What are the roles and responsibilities of an Ethereum Developer?

Ethereum developers work on Blockchain enterprise technology framework design and development solutions. They are responsible for preparing system modules, design documents, and system testing documents as per project requirements. He also works on system architecture and the implementation of the blockchain program function module. He participates in the design of security protocols and architecture.

18) Explain DAO.

Decentralized Autonomous Organizations (DAO) is a decentralized organization with one or more smart contracts that can be run by writing a program deployed on the Ethereum Blockchain platform. 

DAO eliminates the need for third-party involvement as it is owned globally by every token holder. 

19) Explain how PoW consensus works.

The central principle behind PoW consensus is to solve complex mathematical problems and make the largest number of guesses as quickly as possible. Such requires a lot of computational power, and by using a more efficient mining machine to run calculations, a miner can maximize profitability in terms of crypto rewards. 

In this type of consensus mechanism, miners compete to be the first one to find a hash regarding a particular block, which can only be solved using sheer computing power to make the largest number of guesses. When a miner finds the right solution, they advertise it to the whole network, receiving a reward in cryptocurrency provided by the protocol. 

20) Explain the Concept of PoS

Proof-of-Stake is a consensus algorithm that deals with the main drawbacks of PoW. In this mechanism, every block gets validated before the network adds another block to the blockchain ledger. Unlike PoW, where miners have to solve complex puzzles, in PoS, miners can join the mining process using their coins to stake. It allows users to mine for rewards using very minimal hardware and software resources. Here, the mining capacity of a particular miner depends on how many coins they already have; thus, the more coins one has, the better chances are, which indicates only the richest can have control of the consensus.

21) State the importance of account nonce in Ethereum?

An account nonce determines a transaction counter in each account. It is helpful in preventing replay attacks. 

22) Define MetaMask.

MetaMask is a cryptocurrency wallet and also a web browser extension used to store, send and receive Ethereum and ERC20. 

23) What are Ethereum wallets?

Ethereum wallets are a piece of software that allows users to interact with their Ethereum account. These wallets are essential because before you can start trading Ether, you need to store it somewhere, and there comes the role of wallets.

24) What do you know about hardware Ethereum wallets?

If you want a high level of security, consider using this wallet. These are more secure because they store private keys on a physical chip. Since these wallets do not require an internet connection, they make your funds completely immune from all types of cyber-attacks and hacks. Moreover, such wallets offer multiple ways to access the keys. 

25) What are the types of Ethereum networks that exist?

These are of three types:

  • Private Blockchain Network
  • TestNet: The Test Ethereum Network
  • Live Network: The main Network

26)  Mention some of the popular Blockchain-based smart contracts.

  1. Ethereum
  2. NEM
  3. Hyperledger
  4. EOSIO
  5. RSK

27) Are there any standards for Smart Contracts?

Unlike legal slot machines, there are no standards and no government agencies that test and verify the accuracy of smart contracts. However, a certain level of trust must exist between the contracting parties. 

28) What is the first thing that you must define in a Solidity file?

The version number of Solidity is the first thing you must specify as it reduces incompatibility glitches that can occur while compiling with another version. 

29) Define Remix?

A remix is an online platform for developing smart contracts. You can use solidity programs and develop your own smart contracts.

30) Gas usage in a transaction depends on which factors? Also, tell me how you can calculate the transaction fee?

Gas usage depends upon two factors: the first is the amount of storage, and the second one is a set of instructions used in a smart contract. 

The transaction fee can be calculated by using the following formula:

Ether = Tx Fees = Gas Limit * Gas Price

Concluding Lines

Hope these interview questions and answers will help you to land your dream job as an Ethereum Expert or a Smart Contract Developer.

If you are a beginner and want to get started as a learned and Certified Etherum Expert, you can get enrolled in Blockchain Council.

To get instant updates about Blockchain Technology and to learn more about online Blockchain Certifications, check out Blockchain Council

Top 30 Interview Questions for Ethereum & Smart Contracts



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