Architecture — Vastra Platform

End-to-End System Topology

Vastra Platform routes all traffic through AWS CloudFront with AWS WAF security inspection before serving SPAs or invoking Lambda APIs.

[Route 53 DNS]
       |
  [AWS WAF] (Rate-limiting, Turnstile check, SQLi / XSS protection)
       |
[CloudFront Global CDN]
       |--> S3 Customer SPA Bucket (React 19 customer storefront)
       |--> S3 Admin SPA Bucket (Merchant catalog & operations desk)
       |--> S3 Product Assets (WebP swatches, product photography)
       |
[Amazon API Gateway (HTTP/REST)]
       |
[AWS Lambda Runtime (ARM64 / Node.js 22)]
       |
       |---> [Amazon DynamoDB] (Single-table transactional store)
       |---> [Amazon SES] (Transactional order confirmations & refund notices)
       |---> [Paytm Payment Gateway API] (Order tokenization & refund dispatch)
       |---> [Shiprocket Logistics API] (AWB booking & shipping manifest generation)

DynamoDB Single-Table Schema

To avoid RDS connection pooling overhead and cold-start connection penalties, all entities reside in a single high-performance DynamoDB table.

Entity	Partition Key (PK)	Sort Key (SK)	GSI1-PK / GSI1-SK	Attributes
Product	`PRODUCT#<productId>`	`METADATA`	`CATEGORY#<slug>` / `PRICE#<cents>`	Title, SKU, basePrice, images, stockCount, tags
Product Variant	`PRODUCT#<productId>`	`VARIANT#<variantId>`	`SKU#<skuCode>` / `METADATA`	Color, size, fabric, stockQuantity, priceDelta
Customer Order	`ORDER#<orderId>`	`DETAILS`	`CUSTOMER#<custId>` / `CREATED#<isoDate>`	Items, totalAmount, status, paytmTxnId, shippingAddress
Order Item	`ORDER#<orderId>`	`ITEM#<sku>`	—	Unit price, quantity, color, product title
Inventory Lock	`LOCK#<sku>`	`ORDER#<orderId>`	—	Reserved units, lockExpiresAt (TTL attribute)

Order Lifecycle State Machine

Atomic state transitions ensure no double-charging, no phantom inventory reservations, and 100% automated refund processing.

Checkout & Lock

Customer initiates payment. Inventory reservation lock is created with a 15-minute TTL. Transaction token generated via Paytm API.

Payment Verification

Asynchronous webhook from Paytm received. HMAC checksum validated. If verified, order status updates to CONFIRMED and stock is permanently decremented.

Dispatch & Delivery

Shiprocket AWB generated automatically. Label printed in merchant desk. Customer receives tracking SMS & email.

Cancellation & Refund

If cancelled by merchant or customer, Lambda calls Paytm Refund API. On success, stock units are atomically incremented back to inventory.