Case Study: Solving a Shopify Store's Inventory Crisis

Evergreen Home Goods is a direct-to-consumer brand selling sustainable kitchenware and home accessories. What started as a Shopify-only business grew rapidly into a multi-channel operation selling through their Shopify store, Amazon, a wholesale portal for boutique retailers, and a pop-up shop with a Square POS system. Revenue had tripled in 18 months. But their inventory management had not kept pace, and it was becoming an existential threat to the business.

During the holiday season, Evergreen experienced what their founder called "the worst week of my career." They oversold 340 units of their best-selling bamboo cutting board set across Shopify and Amazon simultaneously. The warehouse had 85 units in stock. They had to cancel 255 orders, issue refunds, and deal with a wave of negative reviews that dropped their Amazon seller rating from 4.8 to 4.3 stars. The estimated revenue loss from that single week was $12,400, and the reputational damage was incalculable.

The Challenge

Evergreen's core problem was that inventory existed in four separate systems with no real-time connection between them. Shopify maintained its own inventory count. Amazon's Seller Central had a different count. The wholesale portal relied on a spreadsheet updated twice daily. And the Square POS at pop-up events synced inventory back to a Google Sheet that someone manually reconciled every evening.

The result was that at any given moment, no single system had an accurate picture of actual available inventory. When a product sold on Amazon, the Shopify count did not adjust for up to six hours, during which time the same unit could be sold again on Shopify. During high-traffic periods like flash sales or holiday shopping, the lag between systems was catastrophic.

"We were spending two hours every morning just trying to figure out what we actually had in stock. Our warehouse manager kept a paper notebook as a backup because she did not trust any of our digital systems. That tells you everything you need to know about where we were."

Beyond overselling, the inventory disconnect created cascading operational problems. Purchasing decisions were based on inaccurate data, leading to both overstocking of slow movers and stockouts of popular items. Warehouse staff received conflicting pick lists from different channels. And customer service spent 30% of their time handling inventory-related complaints rather than building customer relationships.

The Solution

The solution centered on creating a single source of truth for inventory that all channels would read from and write to in near real-time. Rather than replacing any of Evergreen's existing platforms, the automation layer was built to sit at the center, mediating inventory updates between all connected systems.

Architecture of the real-time inventory sync system connecting all four sales channels through a central hub.

The system was built using Make.com as the integration backbone with webhook-triggered workflows for each channel. When a sale occurs on Shopify, a webhook fires immediately and the automation decrements available inventory across Amazon, the wholesale portal, and the Square POS system within 30 seconds. The same logic works in reverse for every channel. Returns and inventory adjustments flow through the same hub, ensuring that the central count always reflects reality.

A critical design decision was the implementation of safety stock buffers. Rather than making 100% of physical inventory available across all channels simultaneously, the system allocates channel-specific reserves based on historical sales velocity. If a product has 100 units available, Shopify might show 45, Amazon 40, and wholesale 15, with the system dynamically reallocating as units sell. This prevents the race condition that caused the original overselling crisis.

The system also integrates with QuickBooks for real-time cost of goods sold tracking and triggers automated low-stock alerts to the purchasing team when any SKU drops below its reorder threshold.

The Results

Evergreen Home Goods ran the new system for 90 days before measuring results. The numbers told a clear story.

• Overselling incidents dropped from 40+ per month to zero. In the first 90 days, not a single oversell occurred across any channel. The safety stock buffer system proved to be the critical safeguard.
• Morning inventory reconciliation eliminated. The two hours spent daily reconciling inventory across systems was completely eliminated, freeing the operations team for strategic work.
• Revenue recovered: $14,200 per month. By eliminating overselling cancellations, reducing stockouts on popular items, and enabling confident promotion across all channels, monthly revenue increased by an average of $14,200.
• Amazon seller rating recovered to 4.7 stars within 60 days as order cancellations stopped and fulfillment reliability improved.
• Customer service time on inventory issues dropped by 82%. Staff redirected that time to proactive customer outreach and upselling.

Key Takeaways

Multi-channel selling requires multi-channel inventory sync from day one. Evergreen grew into multi-channel selling organically, adding channels one at a time without building the infrastructure to connect them. The cost of that approach became apparent only when it nearly sank the business. Any merchant selling on more than one platform should implement centralized inventory management before overselling becomes a crisis.

Near real-time is not real-time, and the difference matters. A six-hour sync interval might seem adequate during normal operations, but during a flash sale or holiday rush, hundreds of units can sell in minutes. Sub-minute sync is not a luxury; it is a requirement for any business with meaningful sales volume.

Safety stock buffers are non-negotiable. Even with real-time sync, race conditions can occur when two channels process simultaneous orders for the last available unit. Channel-specific inventory reserves provide a mathematical guarantee against overselling.

Inventory accuracy unlocks better decisions everywhere. When Evergreen could finally trust their inventory data, purchasing improved, warehouse operations became smoother, and marketing could run promotions with confidence. Accurate inventory is not just an operational concern; it is the foundation for every other business decision.

If your e-commerce business is struggling with inventory accuracy across multiple channels, explore how e-commerce automation and inventory sync solutions can protect your revenue and your reputation.