Lightning POS

Build a point-of-sale app that creates invoices and tracks settlement.

advanced2 weeksproject // lightning-pos

Public lesson — sign in to track progress on this roadmap.

Learning objectives

Create invoices from a backend node
Subscribe to invoice settlement events
Design a cashier UX for pending vs paid

study // plan

Lessons are primers. Start with Step 1 (required reading) when present, then follow the numbered steps in the article. Depth comes from primary sources, labs, reflection, and evidence.

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Step 1 // Required reading

Complete these before the numbered steps in the lesson body. Links are listed here once — not repeated below.

docsProject Spec: Lightning POS
Pull project page — acceptance criteria and submit flow.
boltBOLT11

Reflection prompts

Explain Lightning POS to a teammate without jargon - what problem does it solve?
What would break in production if you misunderstood Lightning POS?
Which BOLT (or implementation doc) is the source of truth for this topic, and what did you verify there?

Lab // Project milestone evidence

Complete Steps 2–4. Ship create invoice → QR → settle (or expire) on Polar/regtest and capture demo evidence before marking complete.

evidence required

Link to public repo or branch
Screenshots or commands proving charge → paid (and expiry path)
Short note of one failure case (duplicate charge, late pay, node down)

A Lightning POS turns protocol knowledge into a merchant tool: show QR, wait for payment, print/mark paid.

Complete Step 1 // Required reading in the study plan above, then continue here. This opens Lightning Projects.

Step 2 — Goal

Create invoice for cart total
Display BOLT11 QR
Detect settlement via websocket/webhook/RPC subscribe
Handle expiry and cancel

Loading diagram…

POS mints invoices and listens until settled or expired.

Done when: You can narrate pending vs paid vs expired without opening the code.

Step 3 — Milestones

Phase	Ship
Milestone A	Backend mint invoice + return bolt11
Milestone B	Cashier UI: QR + pending/paid states
Milestone C	Subscribe to settle; expiry/cancel; idempotent charge keys

Done when: Milestone A works before you polish UI chrome.

Step 4 — Build & evidence (lab)

Implement against /projects/lightning-pos. Capture repo link, happy-path demo, and one failure case.

Common mistakes

Creating a new invoice on every UI refresh
Treating “invoice created” as paid
Blocking the cashier UI on synchronous pay RPCs without a pending state

Done when: Lab evidence is filed.

Next lesson

Node Ops Dashboard — channels, peers, balances, and routing revenue.

build // challenge

project // lightning-pos

./open-spec ./submit

Apply what you learned in a focused build session. Ship something small, test it on regtest, and document your approach before moving on.

progress // sign in

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Phase

Ship

Milestone A

Backend mint invoice + return bolt11

Milestone B

Cashier UI: QR + pending/paid states

Milestone C

Subscribe to settle; expiry/cancel; idempotent charge keys

Step 4 — Build & evidence (lab)

Implement against /projects/lightning-pos. Capture repo link, happy-path demo, and one failure case.

Creating a new invoice on every UI refresh

Treating “invoice created” as paid

Blocking the cashier UI on synchronous pay RPCs without a pending state

Done when: Lab evidence is filed.

Node Ops Dashboard — channels, peers, balances, and routing revenue.

Lightning POS

Learning objectives

Step 1 // Required reading

Reflection prompts

Lab // Project milestone evidence

How to study this lesson

Step 2 — Goal

Step 3 — Milestones

Step 4 — Build & evidence (lab)

Common mistakes

Next lesson

further reading

build // challenge

Lightning POS

Learning objectives

Step 1 // Required reading

Reflection prompts

Lab // Project milestone evidence

How to study this lesson

Step 2 — Goal

Step 3 — Milestones

Step 4 — Build & evidence (lab)

Common mistakes

Next lesson

further reading

build // challenge