Blockchain & Decentralized Systems
Overview
Blockchain technology enables trustless, decentralized computation across networks of mutually distrustful participants. What began as Bitcoin’s distributed ledger has evolved into a rich ecosystem of consensus protocols, smart contract platforms, rollup architectures, and decentralized infrastructure. Understanding blockchain internals is now essential for roles in fintech, infrastructure engineering, distributed systems, and cryptographic research.
Why This Section Matters for Interviews
Blockchain interviews span a unique intersection of distributed systems, cryptography, game theory, and systems engineering. You may encounter blockchain questions for roles at:
- Protocol teams: Ethereum Foundation, Solana Labs, Cosmos, Avalanche
- Infrastructure: Alchemy, Infura, QuickNode, Chainstack
- DeFi/CEX: Coinbase, Binance, Uniswap Labs, Aave
- Enterprise: Chainlink, Polygon, Arbitrum, Optimism
- General SWE: Any company exploring Web3 or distributed trust
Section Map
| File | Topics | Key Systems |
|---|---|---|
| Consensus Mechanisms | PoW, PoS, BFT, HotStuff, Tendermint | Bitcoin, Ethereum, Cosmos |
| Ethereum Internals | State trie, rollups, sharding, Verkle trees | Ethereum, L2s, EIPs |
| Blockchain Security | Reentrancy, bridges, MEV, consensus attacks | DeFi, cross-chain, oracles |
| Decentralized Infrastructure | IPFS, DHTs, DID, modular blockchains | IPFS, Filecoin, Cosmos SDK |
Core Concepts at a Glance
mindmap
root((Blockchain))
Consensus
Proof of Work
Proof of Stake
BFT Variants
Nakamoto Consensus
Data Structures
Merkle Trees
Patricia Tries
Verkle Trees
Execution
Smart Contracts
EVM / WASM
Rollups
Security
Smart Contract Audits
Bridge Exploits
MEV
Infrastructure
P2P Networks
DHTs
Decentralized Storage
Key Trade-offs
| Dimension | Centralized | Decentralized |
|---|---|---|
| Throughput | 10K–1M TPS | 10–100K TPS (with L2s) |
| Finality | Milliseconds | Seconds to minutes |
| Censorship resistance | Low | High |
| Operational cost | OPEX | Token economics / gas |
| Data availability | Controlled | Erasure-coded / DAS |
Prerequisites
- Distributed Consensus — Raft, Paxos, BFT foundations
- Cryptography — Hashing, digital signatures, PKI
- Distributed Systems — CAP theorem, consistency models
Interview Preparation Strategy
- Know the classic results cold: Nakamoto consensus, PBFT, the impossibility trilemma
- Understand Ethereum deeply: State transition function, gas mechanics, EIP-4844, EIP-1559
- Be able to compare: PoW vs PoS trade-offs, optimistic vs ZK rollups, monolithic vs modular
- Think in attacks: Reentrancy, front-running, bridge exploits, data withholding
- Connect to fundamentals: How blockchain consensus relates to FLB/PBFT, how Merkle trees relate to content-addressed storage