Conversational CommerceLive in production

CityXmart: a 41-second WhatsApp checkout

Customers browse the catalogue, fill a cart and pay by UPI without leaving WhatsApp. The store owner gets an alert the moment an order is paid.

Order to paid: 41 Sec
App install: 0 MB

Stack: Meta WhatsApp Business API / UPI webhooks / Node.js / PostgreSQL
IP: Transferred to the client

01 · The challenge

CityXmart runs six neighbourhood grocery stores in Jaipur. Orders arrived by phone. Staff took them down by hand, payment was collected on delivery, and reconciliation happened at the end of the day in a spreadsheet. The owner had no visibility into which store was busy, which products were running low, or whether an order had been paid.

Constraints

Customers would not install a new app; WhatsApp was the only channel they would use
UPI had to be official and reconcilable, so grey payment gateways were ruled out
The store owner needed to manage everything from a phone, not a laptop
The system had to work even if a customer's WhatsApp flow was interrupted mid-order

02 · What we built

AGA built a conversational commerce system inside WhatsApp using the official Meta Business API. Customers browse a catalogue, add items to a cart, receive a UPI payment link, and pay without leaving the chat. The owner receives a WhatsApp alert the moment an order is paid, with the full order detail and the reconciled bank reference. A human handoff system escalates edge cases to store staff.

03 · Architecture

How the system is structured.

Simplified. Implementation details are withheld where they are commercially sensitive.

Conversational Commerce · request flow9 stages

01
WhatsApp message received
Meta Cloud API webhook → our Node.js server
02
Session management
Redis stores cart state across conversation turns
03
Intent parsing
Structured message parsing maps customer input to catalogue actions
04
Catalogue lookup
PostgreSQL product database with store-level inventory
05
Cart operations
Add, remove, update quantities via conversational buttons
06
Payment link
HDFC UPI payment link generated and sent as a WhatsApp message
07
Payment webhook
HDFC webhook confirms payment and marks order paid in database
08
Owner alert
WhatsApp notification to store owner with order summary and bank reference
09
Human handoff
Edge cases escalated to store staff via WhatsApp

04 · Engineering detail

What makes it hold up.

Idempotent webhook handlers, so duplicate payment events never create duplicate orders
Conversation state persisted in Redis with 24-hour TTL to survive interrupted sessions
Graceful degradation: if the payment service is down, the customer is told and the order is queued
Rate limiting on inbound WhatsApp webhooks to prevent abuse
All UPI amounts validated server-side before links are generated
Order state machine with clear transitions: CART → PENDING_PAYMENT → PAID → DISPATCHED

05 · Decision log

Key decisions, and why we made them.

01
Official Meta Business API instead of third-party WhatsApp gateway
Grey gateways are blocked periodically, violate Meta's terms, and cannot be used with UPI payment links officially. The Business API costs more but provides reliability and compliance.
02
HDFC Bank direct integration instead of Razorpay or Stripe
The client had an existing HDFC business account and preferred direct bank reconciliation. HDFC's webhook API provided the settlement reference needed for accounting.
03
Redis for session state instead of database
Conversation state is temporary and high-frequency. Redis provides sub-millisecond reads and automatic TTL expiry without accumulating stale session rows in the main database.

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