Multi-Location Inventory: The Strategy That Actually Works

Note: Client names and some details have been changed to protect confidentiality. The technical challenges and solutions are real.

After implementing multi-location inventory for retailers with 3-10 locations, I've learned one thing: the complexity isn't in the technology — it's in the business rules.

Every retailer thinks their inventory is "simple." Then you discover the exceptions.

Solution Comparison

The Real Challenges

1. Race Conditions

Customer buys last item online while another customer checks out in-store with the same item.

With apps: Both sales complete. One customer gets refund email 15 minutes later.

With custom middleware: Database transaction locks inventory. Second sale fails at checkout with "just sold out."

2. Location Priority Logic

Not all locations are equal:

class LocationPriorityService
{
    public function getFulfillmentLocation(Order $order): Location
    {
        $available = $this->getLocationsWithStock($order);

        // VIP customers get closest location
        if ($order->customer->tier === 'vip') {
            return $this->getClosestLocation($order->shippingAddress, $available);
        }

        // Default: lowest shipping cost
        return $this->getCheapestShippingLocation($order, $available);
    }
}

Apps can't implement this. It's your business logic.

3. Channel-Specific Availability

Different channels see different inventory:

• Online store: 80% of warehouse
• Retail stores: Their allocated stock only
• Wholesale: Reserved pool only

This isn't configuration — it's code.

When Apps Fail

Black Friday Disaster: Fashion retailer, 4 locations, premium inventory app ($299/month). Traffic spiked 4x. Sync lagged 30+ minutes. 340 units oversold. Cost: $47,000.

Root cause: App hit Shopify API rate limits. Queue backed up.

The Architecture That Works

Sales Channels (Shopify, Lightspeed A, Lightspeed B)
                    ↓ Webhooks
        Inventory Middleware (Laravel)
    [Ledger] [Allocation Rules] [Routing Logic]
                    ↓
            All Inventory Systems

Key principles:

1. Single source of truth — middleware database
2. Atomic transactions — database locks prevent races
3. Business rules in code — not app configuration
4. Audit everything — full history for reconciliation

The Cost Math

At 100 orders/day across 3 locations with $200 average order:

• 1% overselling rate = $600/day = $18,000/month
• Custom middleware: $35K + $1K/month

Custom pays for itself in under 2 months of prevented overselling.

Getting Started

Under 50 orders/day with 2 locations: Start with native Shopify.

50-200 orders/day with 3+ locations: Evaluate custom middleware now.

Already been burned: Stop patching apps. Build properly.

Need Multi-Location Inventory Help?

We can help you figure out the right architecture for your specific operation.