Blockchain

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.