> ## Documentation Index
> Fetch the complete documentation index at: https://docs.usecharlie.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Overview
> Understand how fulfillment constraints control which locations can fulfill orders
Fulfillment constraints are business rules that **block** locations from fulfilling specific orders. When a constraint applies, the affected locations are completely removed from consideration during checkout.
Constraints are "hard" rules. If the only location with available stock is blocked by a constraint, the customer will see an error and no shipping options will appear at checkout.
## Constraints vs order routing
Charlie offers two ways to control where orders are fulfilled from:
| | Fulfillment constraints | Order routing rules |
| ----------------- | ------------------------------------- | --------------------------- |
| **Effect** | Blocks locations entirely | Deprioritizes locations |
| **When no match** | Checkout blocked, no shipping options | Falls back to next priority |
| **Use case** | Hard business requirements | Optimization preferences |
Use constraints when a location **must not** fulfill certain orders under any circumstances. Use order routing when you **prefer** certain locations but can accept alternatives.
## How constraints work
When a customer reaches checkout, Charlie evaluates each constraint rule against the cart. For every rule that matches:
1. The specified locations are removed from the eligible fulfillment pool
2. Shopify then checks inventory only at remaining locations
3. If no remaining location has stock, checkout is blocked
```mermaid theme={"system"}
flowchart LR
A[All locations] --> B{Constraint
matches?}
B -->|Yes| C[Remove from pool]
B -->|No| D[Keep in pool]
C --> E[Remaining locations]
D --> E
E --> F{Stock
available?}
F -->|Yes| G[Shipping options shown]
F -->|No| H[Checkout blocked]
```
When checkout is blocked, customers see an error message indicating which items cannot be shipped:
## Constraint types
Charlie supports three types of constraints, each triggered by different conditions:
Block locations based on **what** is in the cart (specific products or collections)
Block locations based on **who** is buying (B2B customers, customer tags)
Block locations based on **cart properties** (total quantity, total amount, line item attributes)
## Filtering locations
Each constraint rule specifies which locations to block using one of these filters:
| Filter | Description | Example |
| ---------------------- | ------------------------------------------- | ----------------------------------------- |
| **Specific locations** | Block or allow only named locations | "Block fulfillment from Paris Store" |
| **Location tags** | Block or allow locations by tag | "Block all locations tagged `no-fragile`" |
| **Location type** | Block or allow by type (Store or Warehouse) | "Block all Stores, allow only Warehouses" |
You can choose to either:
* **Exclude** matching locations (block them)
* **Include** only matching locations (block everything else)
Before using constraints, make sure your [locations are properly configured](/locations/overview) with the right types and tags.
## Disabling all constraints
If you need to turn off all active constraints at once, go to **Charlie → Fulfillment constraints** and click **Disable all** at the top of the page.
A confirmation modal shows which rules will be affected:
* **Blocking rules** (safety stock, location capacity) switch to prioritize mode
* **Configurable rules** and **shipment limit** rules are removed
This is useful for troubleshooting checkout issues or temporarily lifting all restrictions during peak periods.
## Use cases
### Bulky items from small stores
A fashion retailer sells oversized dresses that require large packaging. Their smaller retail locations don't have the storage space or packaging materials to ship these items.
**Setup:**
* Constraint type: Product rule
* Condition: Cart contains products from the "Bulky Dresses" collection
* Filter: Exclude locations tagged `small-store`
**Result:**
* Regular items → All locations eligible
* Bulky dresses → Only large stores and warehouses can fulfill
* If only a small store has a bulky dress in stock → Checkout blocked
### High-value orders from warehouse only
A luxury brand wants to ensure that high-value orders (over €500) are only fulfilled from their central warehouse where they have dedicated packaging and insurance processes.
**Setup:**
* Constraint type: Cart rule
* Condition: Total amount > €500
* Filter: Include only locations tagged `central-warehouse`
**Result:**
* Orders under €500 → All locations eligible
* Orders over €500 → Only the central warehouse can fulfill
* If central warehouse is out of stock on a €600 order → Checkout blocked
### B2B orders from dedicated locations
A wholesaler needs to ensure B2B customers are only served from locations with proper invoicing and bulk packaging capabilities.
**Setup:**
* Constraint type: Customer rule
* Condition: Customer is B2B
* Filter: Include only locations tagged `b2b-enabled`
**Result:**
* Regular customers → All locations eligible
* B2B customers → Only B2B-enabled locations can fulfill
* If no B2B location has stock → Checkout blocked