Problem
A brand sells the same products on Trendyol and its own Shopify store, but the catalogs are disconnected. Shopify product updates break mappings, and customer reviews collected on Trendyol never reach the storefront. That leaves valuable social proof confined to the marketplace.
Several live Shopify stores shared this need, each with its own Admin API connection.
Solution
I designed a multi-store custom app in Node.js and TypeScript, with a Next.js interface and Firebase Cloud Functions. It maps Trendyol products to Shopify catalog data and automatically transfers eligible reviews to the matching products.
Synchronisation runs through three mechanisms:
- Event-driven - Shopify product creation, update and deletion webhooks, along with app uninstall events, are processed immediately.
- Scheduled - The Trendyol API is polled regularly to capture changes outside webhook coverage.
- Manual - The operations team can trigger synchronisation when needed.
State and mappings are stored in Firestore. Separate Admin API connections let one installation serve multiple live stores in parallel. I also added international shipping cost information before checkout so customers see the cost earlier.
I developed and deployed JavaScript and TypeScript Shopify Function extensions using Shopify CLI. GraphQL input queries and shopify.extension.toml configuration connect them to the production release workflow.
Result
The system runs in production across multiple Shopify stores. Reviews from Trendyol now appear on each brand's own storefront, and catalog mappings stay current as products change without manual intervention.