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There is no single owner of all data in a headless ecommerce stack. The answer depends on what “owns” means: privacy law assigns roles such as controller and processor, while the technical design assigns a system of record for each kind of data and stage of a workflow. Those assignments can differ, and headless architecture alone decides neither.
Two different meanings of data ownership
Legal responsibility for processing
Privacy laws commonly distinguish the party that determines why and how personal data is processed—the controller or, in some laws, the business—from a processor or service provider that processes data on another party’s behalf. The applicable law, actual processing, and contract matter; a platform’s architecture does not settle the legal roles.
For example, Shopify’s Data Processing Addendum describes the merchant as controller and Shopify as processor for covered customer personal data, subject to exceptions. commercetools’ DPA says that, as between the parties, the customer is controller and commercetools processes personal data on the customer’s behalf or instructions. These are contractual descriptions for the covered relationships, not universal determinations of every party’s role for every service.
Technical authority over records
In an implementation, “ownership” often means which system is authoritative for a particular field or workflow: which application can make the definitive update, and which connected applications merely receive copies. A CRM can be authoritative for customer contact details while a commerce platform handles checkout and an ERP or order management system controls fulfillment. One system need not master every domain.
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What Shopify’s terms say—and where the role can change
Shopify’s DPA generally frames merchants as controllers and Shopify as processor for covered customer personal data, but it specifies important boundaries. For Enhanced Services described in Appendix E, Shopify says it acts as a controller or business for processing that includes providing, developing, and improving analytics, product customization, advertising, and other services using customer interactions and transactions across the merchant’s store, other merchants, and Shopify. The DPA says Shopify Network Intelligence can be disabled, though some apps or features may then be unavailable. The exact scope depends on the current DPA and services enabled for the merchant.
The DPA also says it does not apply to personal data Shopify receives through a customer’s direct relationship with Shopify via services such as Shop and Shop Pay. Thus, “the merchant controls all customer data” is too broad as a blanket statement.
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Commercial responsibility is related but distinct. Shopify’s merchant terms identify the merchant as seller and merchant of record for sales and make the merchant responsible for its store, materials, and transaction handling. Shopify’s guidance also says merchants retain independent privacy and data-protection obligations. The merchant terms, DPA, and applicable law should be considered together; being the seller does not by itself answer every privacy-role question.
How to assign a system of record in a composable stack
Composable commerce guidance illustrates why authority should be decided by domain and lifecycle stage rather than by naming one platform the owner of everything.
| Data or workflow | Common authority described in the guidance | Important boundary |
|---|---|---|
| Customer profile and contact details | A CRM commonly owns the profile. commercetools may own it if no CRM masters it. | A Customer record may still need to exist in commercetools for permissions, cart and order assignment, and personalized promotions. |
| B2B account structure and commercial terms | An ERP commonly owns account hierarchies, credit limits, and payment terms. | The implementation must identify how those records are represented and synchronized in connected systems. |
| Checkout order and contents at capture | The commerce platform—in the cited example, commercetools—owns order capture and contents at checkout. | Authority may move to another system for later order operations. |
| Fulfillment, shipments, cancellations, and returns | An OMS or ERP typically owns the post-capture fulfillment lifecycle. | Define when the handoff occurs and which system’s status is authoritative. |
| Inventory | Inventory commonly follows the system that owns the order lifecycle. | Platform-side inventory tracking is optional in the cited guidance; the actual master depends on the design. |
These examples come from the commercetools integration guide. They describe common patterns, not mandatory allocations for every merchant or a legal ruling about data ownership.
Decide authority and handoffs before integrating
For every data domain, document the authoritative system and the rules around it. At minimum, make separate decisions for customer profiles and contact details, consent and preferences, B2B accounts and payment terms, product catalog, cart, checkout and captured order, fulfillment and returns, inventory, and analytics or event data. The exact master for several of these domains is implementation-specific.
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- Name the authority: Identify the system that holds the definitive record at each lifecycle stage, and distinguish it from systems that store a copy.
- Define who can write: List which applications may create or change a record, and whether updates from a non-master system are rejected, queued, or routed to the authority.
- Specify synchronization: Document the event, API, or other handoff that propagates changes, including expected behavior when an integration is unavailable.
- Set conflict rules: Decide how disagreements are resolved—for example, whether the master always wins or whether a particular field has a separate authority.
- Map retention and deletion: Establish how long records remain and how deletion or correction is carried through connected systems and backups as required by the applicable rules.
- Plan privacy requests: Work out how access, correction, deletion, and export requests reach each system that holds relevant data.
- Plan for exit: Specify what happens to records, copies, and access when a vendor relationship ends.
What to check when evaluating a platform or design
- Role allocation: Which party determines purposes and means for each processing activity? Are any services treated differently from the platform’s ordinary processor role?
- Service scope and data use: What data is used for analytics, advertising, personalization, or services spanning merchants? Which settings and notices apply?
- Record authority: Which system is authoritative for each domain and lifecycle stage, and which systems hold copies?
- Rights and lifecycle operations: How will notices, rights requests, retention, deletion, and vendor termination work across the platform and integrations?
- Integration resilience: What happens when connected systems disagree or an application is unavailable, and how are missed updates reconciled?
For Shopify merchants, the platform’s help center says, “You’re generally the controller of your customers’ data.” Its privacy guidance also says, “Shopify provides the technology that powers your store, but any contract of sale with customers on your store is between you and your customer.” These are Shopify’s descriptions of its services and merchant relationship, not a substitute for the applicable contract or legal advice. See Shopify’s GDPR guidance and its privacy and data-protection guidance.
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For a real merchant, determine privacy roles from the current contract and DPA, the services actually used, the data flows, and the jurisdictions involved. Determine technical authority separately by assigning each record and lifecycle stage to a system, then documenting how updates, rights requests, and vendor exit are handled. Neither a headless setup nor a seller-of-record designation answers both questions on its own.
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