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.