What we have built up to keep large-scale commerce
running on Shopify Plus

In large-scale commerce, Shopify, ERP, WMS, OMS, payment and in-store systems all operate as one chain, which makes data consistency fragile from order creation through inventory allocation, payment and fulfilment. The point is not to consolidate everything into Shopify, but to decide which system owns what, and in which order things are processed. Flagship draws the line between Shopify Plus standard features and custom development, and designs the system as a whole — core systems, inventory and payments included.

Porting every existing feature into Shopify is not the goal. We identify which requirements the business genuinely needs, then separate what Shopify’s standard features can carry from what calls for custom design and development. Carry over every legacy specification and you lose Shopify’s advantages; lean too heavily on standard features and day-to-day operations stop working. Designing that boundary is where architecture for large-scale commerce begins.

Where we build custom, we design the processing order and data consistency of orders, inventory and payments. From order creation to inventory allocation to payment handed off for fulfilment, the structure has to keep data consistent across multiple systems. For WMS, OMS, ERP and order-management integrations, we handle everything in-house, from integration design through connector development.

For an apparel brand with physical stores across Japan, our Shopify Plus build implemented real-time store inventory display and buy-online-pickup-in-store (BOPIS) ahead of Shopify’s official support, going from design kick-off to release in four months.

What we cover

• Shopify Plus architecture design, and the split between standard features and custom development
• Sequence design for orders, inventory and payments, with data consistency guaranteed
• Data integration and connector development for WMS, OMS, ERP and order-management systems
• Real-time store inventory display and buy-online-pickup-in-store (BOPIS)
• Load testing and resilience design for large sales events and traffic spikes

Migrating large-scale commerce is hard because it is not only screens and product data that move: post-order operations, core-system integrations, customer accounts and existing URLs all have to come with it. Rather than reproducing the current system as-is, we identify the operations that cannot stop and redesign around what Shopify Plus does well.

For a storefront rebuild or a cart migration, we start by taking stock of current operations and pinpointing the processes and integrations the business cannot run without. Alongside migrations from existing platforms such as ecbeing, Salesforce Commerce Cloud (SFCC) and EC-CUBE, we have redesigned and migrated operations that had been running on Microsoft Access.

A migration does not always switch everything at once. We get the commercial core working first — browsing, cart, checkout, payment and order creation — while loyalty programmes and advanced marketing integrations may follow in stages. Deciding what belongs in the first release and what moves to a later phase is one of the defining judgements in migration design.

Data migration for customers, orders and products sits in the same project as the existing core-system integrations. Replacing the storefront alone is not a completed migration if post-order operations and data flows cannot continue.

Migration from legacy customer accounts to new customer accounts has become increasingly common. Because sign-in moves from a password to a one-time code sent by email, the switch has to be designed with the retirement of the old accounts in mind. We have run such cut-overs during quiet daytime hours with no service downtime and no overnight maintenance window.

What we cover

• Taking stock of current operations and redesigning the commerce architecture around Shopify Plus
• A phased migration plan that prioritises browsing, cart, checkout, payment and order creation
• Migration of customer, order and product data
• Migration to Shopify from ecbeing, Salesforce Commerce Cloud, EC-CUBE and other existing platforms
• Switching from legacy customer accounts to new customer accounts

Flagship understands how enterprise IT projects run — requirements definition, security review, parallel work with multiple vendors, cut-over — and is set up to keep large-scale software development moving as a project.

We work through project management that does not depend on any one individual. Requirements and the reasoning behind decisions are recorded, so the context survives a change of personnel.

One co-development engagement has continued for more than six years of maintenance and enhancement work since the original contract. Even on projects running in parallel with core-system or POS replacements and several vendors, we support delivery through to cut-over, including the coordination with surrounding systems.

The clients we work with are businesses, not consumers. We take the time to understand the brand, the products and the operations, and we start by deciding together what should be built before development begins. We have also taken on projects that had previously stalled, restructured them around an understanding of the business, and launched them in stages.

What we cover

• Requirements definition and security review for enterprise engagements
• Managing projects that run in parallel with multiple vendors, through to cut-over
• Project management that does not depend on any single individual
• Post-launch maintenance and enhancement development (scrum-based collaboration)
• Understanding the business and its operations before development starts

Cross-border commerce takes more than multiple languages and currencies. Duty and import-tax calculation based on HS codes and country of origin, display and collection at checkout, carrier integration, fulfilment locations, inventory and returns are all connected within a single transaction. Using Shopify Markets and Global-e, we design duty handling — including DDP (Delivered Duty Paid: duties and import taxes shown and collected at purchase, then remitted and shipped under the seller’s responsibility) — international shipping and multi-location inventory as one system.

Design starts with deciding where responsibility for duties and shipping sits. Are duties collected at purchase under DDP, or paid by the recipient on arrival? Which location ships the order, and where do returns go back to? That decision determines what checkout displays, how carriers are integrated, the order in which inventory is allocated, and how the accounting works. Country-level localisation through Shopify Markets — language, currency and tax rates — and integration with cross-border services such as Global-e are layered on top of it.

Projects that implement Japan-specific requirements on top of a global platform run by an overseas head office follow the same approach. We design how requirements such as hemming, gift wrapping, discount constraints and phonetic name fields can sit on the shared platform without breaking it, and we take on knowledge transfer and technical leadership for the maintenance vendor. English is the working language at Flagship, so we handle requirements definition and project delivery with overseas head offices directly.

For a major music company selling internationally we built country-level localisation with centralised multi-location inventory and automated fulfilment. For a Japanese fashion brand selling overseas we built a cross-border store integrated with their inventory system and supporting multiple languages and currencies.

What we cover

• Country-level localisation through Shopify Markets (language, currency, tax rates)
• Duty and import-tax calculation from HS codes and country of origin, with DDP collection at purchase and international shipping
• Centralised multi-location inventory, automated fulfilment, and logistics flows including returns
• Integration with cross-border services such as Global-e
• Japan-specific requirements on global platforms, with requirements definition in English with overseas head offices