Blockchain Interview questions

Interviewing people for blockchain roles? Applying for blockchain jobs? These are some of the top interview questions right now.

1. What is a blockchain?
2. Why are blockchains often referred to as distributed ledger technologies (DLT)?
3. What is proof of work/proof of stake/proof of elapsed time etc.?
4. What is a consensus algorithm and why is it useful in blockchain?
5. Explain the common consensus algorithms (e.g. Paxos, Raft, Tangeroa, PBFT, RBFT, BFTsmart etc)
6. What is hashing/hash functions and how are they used in blockchain?
7. Give me an overview of Bitcoin.
8. What is mining? How does it work in Bitcoin?
9. What is the difference between Bitcoin and Ethereum?
10. What are smart contracts? Do you know a smart contract language (Solidity / Serpent / Vyper) ?
11. How does Hyperledger Fabric work?
12. What are some common privacy modes in blockchain (e.g. encrypted on chain data, channels in hyperledger fabric, R3 Corda privacy model)
13. What is the difference between a public blockchain and private/consortium blockchains? Pros and cons?
14. What is an ICO?
15. What is a token?
16. What is an ERC20 contract?
17. What is a Merkle tree/trie and how is it used in blockchain?
18. Explain how public / private digital signatures work.
19. Explain the difference between symmetric and asymmetric key encryption?
20. How does Diffie Hellman key exchange work in SSL? What is it used for?
21. What scalability and throughput challenges are there with blockchain? What solutions would you suggest?