2nd/10_Wiki/Topics/AI_and_ML/Point-of-Sale.md

---
id: wiki-2026-0508-point-of-sale
title: Point of Sale
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [POS, retail-pos, payment-terminal]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [retail, payments, pos, square, stripe]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: TypeScript
  framework: Stripe Terminal / Square API
---

# Point of Sale (POS)

## 매 한 줄
> **"매 retail transaction 의 capture system — 매 hardware + software + payments + analytics"**. 매 cash register → ECR (1970s) → cloud POS (Square 2009, Toast 2011, Shopify POS) → 매 modern unified commerce (online + offline + AI inventory + loss prevention).

## 매 핵심

### 매 components
- **매 hardware**: terminal (iPad/Android), card reader (chip + tap + Apple Pay), receipt printer, cash drawer, barcode scanner, kitchen display.
- **매 software**: catalog, cart, tax, discounts, tips, split bill, refunds, customer profiles, inventory.
- **매 payments**: card-present (EMV chip + NFC), digital wallets (Apple Pay, Google Pay), QR (Alipay, WeChat), BNPL (Klarna, Afterpay).
- **매 analytics**: sales dashboards, item performance, employee performance, demand forecast.
- **매 integrations**: accounting (QuickBooks), payroll, e-commerce (Shopify), marketing (loyalty, SMS).

### 매 modern players (2026)
- **매 Square** (Block): SMB-focused, Cash App integration, free entry POS.
- **매 Stripe Terminal**: developer-first, omnichannel API, embedded readers.
- **매 Toast**: restaurant-vertical, kitchen ops, payroll.
- **매 Shopify POS**: omni-commerce (online + retail unified inventory).
- **매 Lightspeed**: retail/restaurant/golf vertical.
- **매 Clover** (Fiserv): bank-distributed, app marketplace.
- **매 SumUp / iZettle**: Europe SMB.

### 매 AI/ML in POS (2026)
- **매 loss prevention**: computer vision 매 self-checkout 매 mis-scans (Everseen, Diebold, Mashgin Vision).
- **매 demand forecasting**: per-SKU per-store sales prediction (XGBoost/transformer).
- **매 dynamic pricing**: 매 perishables markdown optimization.
- **매 fraud detection**: 매 chargeback prediction, 매 stolen card flagging.
- **매 voice ordering / AI drive-thru**: McDonald's, Wendy's deployments.
- **매 visual search**: scan product 매 photo 의 lookup.

### 매 standards / compliance
- **매 PCI-DSS**: card data handling.
- **매 EMV**: chip card protocol.
- **매 P2PE**: point-to-point encryption.
- **매 tokenization**: store token, not PAN.
- **매 SOC 2**: SaaS POS providers.

### 매 응용
1. 매 retail (apparel, grocery, c-store).
2. 매 restaurants (QSR, FSR, food trucks).
3. 매 services (salons, mobile contractors).
4. 매 events / pop-ups (mobile readers).

## 💻 패턴

### Stripe Terminal — collect in-person payment
```typescript
import { loadStripeTerminal } from "@stripe/terminal-js";

const StripeTerminal = await loadStripeTerminal();
const terminal = StripeTerminal.create({
  onFetchConnectionToken: async () => {
    const r = await fetch("/connection_token", { method: "POST" });
    return (await r.json()).secret;
  },
  onUnexpectedReaderDisconnect: () => console.warn("disconnected"),
});

const discoverResult = await terminal.discoverReaders();
await terminal.connectReader(discoverResult.discoveredReaders[0]);

// Server creates PaymentIntent, client collects
const { paymentIntent } = await fetch("/create_pi", {
  method: "POST", body: JSON.stringify({ amount: 1999 }),
}).then(r => r.json());

const result = await terminal.collectPaymentMethod(paymentIntent.client_secret);
const confirmed = await terminal.processPayment(result.paymentIntent);
console.log("paid:", confirmed.paymentIntent.id);
```

### Square Terminal API
```javascript
const { Client, Environment } = require("square");
const client = new Client({
  accessToken: process.env.SQUARE_TOKEN,
  environment: Environment.Production,
});

const checkout = await client.terminalApi.createTerminalCheckout({
  idempotencyKey: crypto.randomUUID(),
  checkout: {
    amountMoney: { amount: 1999n, currency: "USD" },
    deviceOptions: { deviceId: "DEVICE_ID" },
  },
});
```

### Catalog + tax calculation
```typescript
type Item = { id: string; name: string; price_cents: number; tax_rate: number; sku: string };

function calculateOrder(items: Item[], qty: Record<string, number>, discount_cents = 0) {
  const subtotal = items.reduce((s, it) => s + it.price_cents * (qty[it.id] ?? 0), 0);
  const tax = items.reduce((s, it) =>
    s + it.price_cents * (qty[it.id] ?? 0) * it.tax_rate, 0);
  const total = subtotal + tax - discount_cents;
  return { subtotal, tax, discount: discount_cents, total };
}
```

### Receipt printer (ESC/POS)
```javascript
// node-thermal-printer
const { ThermalPrinter, PrinterTypes } = require("node-thermal-printer");
const printer = new ThermalPrinter({
  type: PrinterTypes.EPSON,
  interface: "tcp://192.168.1.100",
});
printer.alignCenter(); printer.println("ACME COFFEE");
printer.drawLine();
printer.tableCustom([
  { text: "Latte x2", align: "LEFT" },
  { text: "$10.00", align: "RIGHT" },
]);
printer.drawLine();
printer.println("TOTAL: $10.80");
printer.cut(); await printer.execute();
```

### EMV / NFC reader (BBPOS via Stripe)
```typescript
// 매 Stripe Terminal SDK 매 BBPOS WisePOS E / Stripe Reader S700
// 매 PCI-DSS scope 의 reduce — 매 reader 매 PAN 의 handle, 매 server 매 token 의 receive
const reader = await terminal.connectReader(readers[0], { fail_if_in_use: true });
```

### Inventory sync (Shopify POS)
```javascript
// Shopify Admin API — unified inventory across channels
const res = await fetch(`https://${SHOP}.myshopify.com/admin/api/2025-01/inventory_levels/adjust.json`, {
  method: "POST",
  headers: { "X-Shopify-Access-Token": TOKEN, "Content-Type": "application/json" },
  body: JSON.stringify({
    inventory_item_id: 12345,
    location_id: 67890,
    available_adjustment: -1,  // sold one
  }),
});
```

### Loss prevention (CV self-checkout)
```python
# 매 simplified pseudocode — 매 actual: YOLOv8 + tracking + match to scanned barcode
import cv2
from ultralytics import YOLO

model = YOLO("yolov8n.pt")
cap = cv2.VideoCapture(0)
scanned_skus = set()  # populated by barcode scanner events

while True:
    ret, frame = cap.read()
    detections = model(frame)[0]
    visible_items = {classify_to_sku(d) for d in detections.boxes}
    discrepancy = visible_items - scanned_skus
    if discrepancy:
        alert_associate(f"Unscanned: {discrepancy}")
```

### Webhook — payment.succeeded
```typescript
// 매 Stripe webhook 의 receive — 매 settle order in DB
import express from "express";
const app = express();
app.post("/webhook", express.raw({ type: "application/json" }), async (req, res) => {
  const sig = req.headers["stripe-signature"]!;
  const event = stripe.webhooks.constructEvent(req.body, sig, WEBHOOK_SECRET);
  if (event.type === "payment_intent.succeeded") {
    const pi = event.data.object;
    await db.orders.update({ stripe_pi: pi.id }, { status: "paid" });
  }
  res.json({ received: true });
});
```

## 매 결정 기준
| 상황 | Solution |
|---|---|
| 매 SMB cafe / pop-up | 매 Square |
| 매 restaurant chain | 매 Toast |
| 매 omni-commerce retail | 매 Shopify POS |
| 매 dev-first / custom UX | 매 Stripe Terminal |
| 매 enterprise multi-store | 매 NCR / Oracle Symphony |
| 매 EU SMB | 매 SumUp / iZettle |
| 매 unattended kiosk / self-checkout | 매 Mashgin / Toshiba + Stripe |

**기본값**: 매 Stripe Terminal (developer-first, custom flow) 또는 매 Square (turnkey SMB).

## 🔗 Graph
- Adjacent: [[Shopify]]

## 🤖 LLM 활용
**언제**: 매 receipt parsing, 매 customer Q&A chatbot, 매 menu generation, 매 anomaly summary 의 사용.
**언제 X**: 매 payment authorization (deterministic flow), 매 PII handling (compliance risk).

## ❌ 안티패턴
- **매 store full PAN**: 매 PCI-DSS violation. 매 token 만 store.
- **매 home-grown payment terminal**: 매 EMV cert 매 expensive — 매 SaaS provider 의 사용.
- **매 ignore offline mode**: 매 retail Wi-Fi 매 unstable — 매 store-and-forward needed.
- **매 monolithic POS**: 매 vertical lock-in — 매 API-first (Stripe/Shopify) 의 prefer.
- **매 no idempotency keys**: 매 double-charge risk on retry.

## 🧪 검증 / 중복
- Verified (Stripe Terminal docs, Square API, Shopify Admin API, PCI-DSS v4.0).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Stripe/Square/Shopify patterns + AI loss prevention |