a Canadian industrial distributor

Shopify and Amazon Marketplace Synchronization

Keeping inventory, pricing, and listings consistent across Shopify and Amazon SP-API.

Employer details in this case study are anonymized to protect proprietary business information. Architecture, decisions, and results are presented as accurately as possible.

The problem

Selling the same products on Shopify and Amazon means keeping two independent systems honest with each other. Shopify handled the storefront and source-of-truth inventory; Amazon required its own listings, its own pricing rules, and its own inventory feed through SP-API. Left unmanaged, that gap produces the worst kind of ecommerce failure: an oversell on a marketplace, a listing that's technically live but effectively invisible because pricing or content issues knocked it out of buy box contention, or inventory counts that just quietly drift apart over weeks.

Architecture

Marketplace sync — simplified

Shopify (source of truth)

Inventory, pricing, product data

Reconciliation engine

Diff, match, policy checks

Amazon SP-API

Listings, inventory feeds, pricing

Monitoring

Mismatch + listing-health alerts

What I built

Product matching. Amazon listings get matched back to Shopify SKUs using ASIN/SKU mapping with fallback matching on UPC and title similarity for products without a clean existing mapping — similar in spirit to the matching logic in the catalogue automation pipeline, applied here across marketplace boundaries instead of supplier boundaries.

Inventory reconciliation. A scheduled job compares Shopify's on-hand quantity against what Amazon believes it has, and pushes corrections through SP-API. Discrepancies beyond a normal sync delay get flagged instead of silently corrected, since a persistent mismatch is usually a sign of a deeper problem (a failed feed, a miscounted receiving, a return that didn't reconcile).

Pricing sync with policy awareness. Price updates flow to Amazon through SP-API respecting Amazon's pricing rules (minimum advertised price, fee-aware margin floors) so a Shopify-side sale price can't accidentally violate marketplace policy or tank margin on a high-fee category.

Listing health monitoring. A recurring check watches for listings that dropped out of buy box contention, got suppressed for content issues, or otherwise went quietly invisible — the kind of problem that costs revenue for weeks before anyone notices it manually.

Reliability and validation

Reconciliation runs are diffed and logged before any corrective write, the same discipline used in the catalogue pipeline.
Persistent mismatches (not explained by normal sync latency) escalate to a human instead of being auto-corrected indefinitely.
Pricing changes are checked against marketplace policy constraints before they're sent.
Listing-health checks run on a schedule independent of the sync jobs, so a healthy sync doesn't mask an unhealthy listing.

Business impact

Marketplace expansion is only worth doing if it doesn't create new operational risk. This system let the business list and sell confidently on Amazon without inventory or pricing becoming a manual babysitting job — a necessary piece of the same growth story covered in the catalogue automation case study, where this employer's ecommerce revenue grew from roughly $60,000 to $400,000 per month.

What I'd change next

Buy-box and pricing dynamics on Amazon move faster than a scheduled job can always keep up with — the next iteration I'd build is event-driven reconciliation triggered by Amazon notifications rather than pure polling, to shrink the reaction window further.