Blockchain

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name: "Blockchain" description: "Understand blockchain technology, interact with smart contracts, and evaluate when distributed ledgers solve real problems."

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What This Covers

Blockchain fundamentals and practical interaction — the technology, not the speculation.

In scope: Distributed ledgers, consensus, transactions, smart contract interaction, wallets, token standards. Out of scope: Trading strategies, price analysis, specific DeFi protocols, Solidity development (see dedicated skills).

Core Concepts

| Concept | One-liner | |---------|-----------| | Distributed ledger | Shared database synchronized across nodes, no single owner | | Consensus | How strangers agree on truth without trusting each other | | Immutability | Changing history requires re-doing all subsequent work | | Smart contract | Code that executes automatically when conditions are met | | Gas | Fee paid to network for computation |

For mental models and analogies, see concepts.md.

Developer Quick Reference

// Read contract (viem)
const balance = await client.readContract({
  address: TOKEN, abi: erc20Abi,
  functionName: 'balanceOf', args: [wallet]
})
// Write requires wallet + confirmation wait
const hash = await walletClient.writeContract({...})
const receipt = await client.waitForTransactionReceipt({ hash })

Common traps: missing allowance checks, wrong decimals (ETH=18, USDC=6), not awaiting confirmations.

For full patterns, see dev.md.

When to Use Blockchain

✅ Use when: Multiple parties need shared truth, no trusted authority exists, immutability is critical, settlement costs are high.

❌ Don't use when: Single org controls data, you trust a central authority, data needs deletion (GDPR), or a database solves it.

> The Database Test: Would PostgreSQL with audit logs solve this? If yes, skip blockchain.

For decision framework and enterprise platforms, see evaluation.md.

Security Essentials

Seed phrase = master key — never share, never screenshot

Hardware wallet > software wallet > exchange

Test transactions before large transfers

Verify URLs obsessively — phishing clones are sophisticated

For wallet security and scam patterns, see security.md.