Devinterview-io / blockchain-interview-questions

๐ŸŸฃ Blockchain interview questions and answers to help you prepare for your next data structures and algorithms interview in 2024.

Geek Repo:Geek Repo

Github PK Tool:Github PK Tool

Top 42 Blockchain interview questions and answers in 2021.

You can check all 42 Blockchain interview questions here ๐Ÿ‘‰ https://devinterview.io/data/blockchain-interview-questions


๐Ÿ”น 1. What is blockchain?

Answer:

Blockchain is a secure distributed ledger (data structure or database) that maintains a continuously growing list of ordered records, called โ€œblocksโ€, that are linked using cryptography. Each block contains a cryptographic hash of the previous block, a timestamp, and transaction data.

By design, a blockchain is resistant to modification of the data. It is "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way".

Once recorded, the data in any given block cannot be altered retroactively without alteration of all subsequent blocks, which requires consensus of the network majority.

Source: en.wikipedia.org   


๐Ÿ”น 2. What is blockchain transaction?

Answer:

Transactions are the things that give a blockchain purpose. They are the smallest building blocks of a blockchain system. Transactions generally consist of:

  • a recipient address,
  • a sender address,
  • and a value.

This is not too different from a standard transaction that you would find on a credit card statement.

A transaction changes the state of the agreed-correct blockchain. A blockchain is a shared, decentralized, distributed state machine. This means that all nodes (users of the blockchain system) independently hold their own copy of the blockchain, and the current known "state" is calculated by processing each transaction in order as it appears in the blockchain.

Source: pluralsight.com   


๐Ÿ”น 3. What is proof-of-work?

Answer:

A proof of work is a piece of data which is difficult (costly, time-consuming) to produce but easy for others to verify and which satisfies certain requirements. Producing a proof of work can be a random process with low probability so that a lot of trial and error is required on average before a valid proof of work is generated. Difficulty is a measure of how difficult it is to find a hash below a given target.

Source: en.bitcoin.it   


๐Ÿ”น 4. Why does Blockchain need coins or tokens?

Answer:

Tokens/Coins are used as a medium of exchange between the states. They are digital assets built in to perform a specific function within a blockchain.

When someone does a transaction, there is a change of state, and coins are moved from one address to another address. Apart from that, transactions contain some additional data; this data can be mutated through the change of state. For this reason, blockchains need coins or tokens to incentivize the participants to join their networks.

Source: mindmajix.com   


๐Ÿ”น 5. What is the blockchain data structure?

Answer:

Basically the blockchain data structure is explained as a back-linked record of blocks of transactions, which is ordered. It can be saved as a file or in a plain database. Each block can be recognized by a hash, created utilizing the SHA256 cryptographic hash algorithm on the header of the block. Each block mentions a former block, also identified as the parent block, in the โ€œprevious block hashโ€ field, in the block header.

Source: cryptoticker.io   


๐Ÿ”น 6. What is the purpose of a blockchain node?

Answer:

A blockchain exists out of blocks of data. These blocks of data are stored on nodes (compare it to small servers). Nodes can be any kind of device (mostly computers, laptops or even bigger servers). Nodes form the infrastructure of a blockchain.

All nodes on a blockchain are connected to each other and they constantly exchange the latest blockchain data with each other so all nodes stay up to date. They store, spread and preserve the blockchain data, so theoretically a blockchain exists on nodes.

A full node is basically a device (like a computer) that contains a full copy of the transaction history of the blockchain.

Source: lisk.io   


๐Ÿ”น 7. What is the Genesis Block?

Answer:

The first block in any blockchain is termed the genesis block. If you start at any block and follow the chain backwards chronologically, you will arrive at the genesis block. The genesis block is statically encoded within the client software, that it cannot be changed. Every node can identify the genesis blockโ€™s hash and structure, the fixed time of creation, and the single transactions within. Thus every node has a secure โ€œrootโ€ from which is possible to build a trusted blockchain on.

Source: linkedin.com   


๐Ÿ”น 8. Explain the common structure of blockchains

Answer:

Blockchains are composed of three core parts:

  • Block: A list of transactions recorded into a ledger over a given period. The size, period, and triggering event for blocks is different for every blockchain.
  • Chain: A hash that links one block to another, mathematically โ€œchainingโ€ them together.
  • Network: The network is composed of โ€œfull nodes.โ€ Think of them as the computer running an algorithm that is securing the network. Each node contains a complete record of all the transactions that were ever recorded in that blockchain.
Source: dummies.com   


๐Ÿ”น 9. What is deterministic behavior?

Answer:

If A + B = C, then no matter what the circumstances, A+B will always be equal to C. That is called deterministic behavior.

Hash functions are deterministic, meaning Aโ€™s hash will always be H(A).

Source: blockgeeks.com   


๐Ÿ”น 10. Explain why a blockchain needs tokens to operate

๐Ÿ‘‰๐Ÿผ Check all 42 answers


๐Ÿ”น 11. Why is the blockchain immutable?

๐Ÿ‘‰๐Ÿผ Check all 42 answers


๐Ÿ”น 12. How Are Blockchain And Distributed Ledger Different?

๐Ÿ‘‰๐Ÿผ Check all 42 answers


๐Ÿ”น 13. What is RSA algorithm?

๐Ÿ‘‰๐Ÿผ Check all 42 answers


๐Ÿ”น 14. What is Merkle Trees?

๐Ÿ‘‰๐Ÿผ Check all 42 answers


๐Ÿ”น 15. Explain why there is a fixed supply of bitcoins?

๐Ÿ‘‰๐Ÿผ Check all 42 answers



Thanks ๐Ÿ™Œ for reading and good luck on your next tech interview!
Explore 3800+ dev interview question here ๐Ÿ‘‰ Devinterview.io