Distributed-Ledger Architecture (general)
Generalizes the Bitcoin-specific bitcoin/* skills into engine-agnostic ledger
design. For deep Bitcoin/Lightning specifics, defer to those skills.
First question: do you actually need a ledger?
A ledger is an append-only, replicated, tamper-evident log agreed by mutually-distrusting parties. Use one only when you genuinely have: multi-party lack of trust, a need for shared auditable state, and no acceptable trusted intermediary. If a single org controls the data, a normal (possibly append-only/audited) database is simpler, faster, and cheaper — most "blockchain" projects should be databases.
Consensus family (builds on distributed-consensus)
| Family | Sybil resistance | Trade-off |
|---|---|---|
| PoW | Burn energy | Robust, slow, energy-heavy, probabilistic finality |
| PoS | Stake capital | Efficient, fast finality, weak-subjectivity/validator-set concerns |
| BFT (PBFT/Tendermint) | Known validator set | Fast deterministic finality, bounded validators → more permissioned |
Permissionless (open validator set) favors PoW/PoS; permissioned/consortium favors BFT.
Layering: L1 vs L2
- L1 = base chain (security + data availability). Scaling it directly hits the trilemma.
- L2 moves execution off L1 while inheriting its security:
- Rollups post compressed data + proofs to L1. ZK rollups (validity proofs, fast finality, harder to build) vs optimistic rollups (fraud proofs, challenge window/withdrawal delay).
- State/payment channels (e.g. Lightning) — off-chain bilateral updates, on-chain settlement; great for high-frequency payments.
- Sidechains — own security, bridged; weaker guarantees.
Other decisions
- Permissioned vs permissionless: trust model + regulatory needs.
- State model: UTXO (parallelizable, privacy, harder smart contracts) vs account (stateful contracts, simpler, sequential nonces).
- Trilemma: decentralization / security / scalability — you optimize two; L2s are the usual escape valve.
- Finality: probabilistic (PoW) vs deterministic/instant (BFT) — affects UX and bridge safety.
Guidance
Single trust domain → database. Multi-party, open → permissionless L1 + L2 for scale. Known consortium → permissioned BFT chain. High-frequency payments → channels. Always justify the ledger over a database first.