LND

LND is a widely deployed Lightning implementation with gRPC/REST APIs and macaroon-based auth. Many apps integrate here first.

Why this matters

Production integrations live or die on auth scoping, idempotent payment calls, and careful macaroon storage.

Analogy

Macaroons are VIP wristbands with permissions printed on them. Anyone holding an admin wristband is you, guard them like passwords.

lncli getinfo
lncli addinvoice --amt 1000
lncli payinvoice <bolt11>

Worked mental model

Re-read the diagrams in this lesson once out loud in plain language. If you cannot explain the flow to a friend without jargon, pause and revisit Mastering Bitcoin / Mastering Lightning chapters linked in Resources. Chapter references are intentional, not decorative.

Hands-on habit

Every protocol idea should be paired with one local experiment:

1. Reproduce the happy path on regtest (or Polar for Lightning)
2. Break it on purpose (wrong fee, expired invoice, offline peer)
3. Write down what error you saw and which layer produced it (wallet, node, mempool, peer)

That habit turns reading into builder instinct.

Glossary check

Pick three terms from this lesson and define them in one sentence each without opening notes. Weak definitions mean the lesson is not finished yet.

Resource order

Use Resources in order: narrative book chapter first, then BIP/BOLT for precision, then implementation docs for commands. Jumping straight to RPC flags without the mental model creates brittle knowledge.

Next steps

Compare with Core Lightning’s plugin-centric model.