MACH Architecture Migration: Planning Your Move from Monolithic Commerce

The question facing mid-market and enterprise commerce teams in 2025 is no longer whether composable architecture is viable, but when and how to migrate. Gartner forecasts that 60% of new cloud commerce implementations will use MACH (Microservices, API-first, Cloud-native, Headless) principles by 2027, up from less than 20% in 2022. That trajectory is not speculative. It reflects real procurement decisions being made right now by brands that have hit the ceiling of what their monolithic platforms can deliver.

If you are running Magento, Salesforce Commerce Cloud, SAP Hybris, or a similar all-in-one platform and are beginning to feel the constraints — slow release cycles, inflexible pricing models, painful integrations, rising total cost of ownership — this guide is for you. We will walk through how to evaluate whether migration is right for your business, how to plan it in phases, how to restructure your team, and how to build the business case that gets the project approved.

At McKenna Consultants, we have delivered composable commerce implementations for B2B and B2C organisations using Elastic Path as the commerce engine. This article draws on that practical experience.

Why Monolithic Platforms Create a Ceiling

Monolithic commerce platforms were designed for a world where “the website” was the only digital sales channel. They bundle the storefront, product catalogue, cart, checkout, pricing engine, CMS, and often the OMS into a single deployable unit. That coupling made sense when digital commerce was relatively simple.

The problem emerges when business requirements outgrow the platform’s assumptions. Common pain points include:

• Pricing complexity. B2B contract pricing, volume tiers, customer-specific catalogues, and multi-currency support are bolted on rather than natively supported. Customisations become fragile and expensive to maintain.
• Channel proliferation. You need to sell through a website, a mobile app, a marketplace, an in-store kiosk, and a sales rep portal. The monolith’s tightly coupled frontend makes this extraordinarily difficult.
• Release velocity. Changes to the checkout flow require a full regression test of the entire platform. Deployment windows shrink. Innovation stalls.
• Integration brittleness. Connecting the platform to ERP, PIM, WMS, and marketing automation systems requires custom middleware that becomes its own maintenance burden.
• Vendor lock-in. The platform vendor controls your upgrade path, your hosting costs, and increasingly your feature roadmap. Strategic flexibility erodes over time.

These are not theoretical objections. They are the reasons that organisations with complex commerce requirements are actively evaluating MACH architecture migration planning as a strategic initiative.

What MACH Architecture Actually Means

Before diving into migration planning, it is worth being precise about what MACH means in practice.

Microservices

Each business capability — product catalogue, pricing, cart, checkout, search, CMS — is a separate, independently deployable service. You can update your search engine without touching your checkout. You can replace your CMS without affecting your product catalogue.

API-First

Every service exposes a well-documented API as its primary interface. The frontend, back-office tools, and third-party integrations all consume the same APIs. There is no “back door” that bypasses the API layer.

Cloud-Native

Services run on managed cloud infrastructure with auto-scaling, redundancy, and global distribution. You are not managing servers. The commerce engine vendor handles uptime, security patches, and infrastructure scaling.

Headless

The presentation layer is completely decoupled from the commerce engine. Your frontend team builds the customer experience using whatever framework suits the channel — React, Next.js, Vue, or a native mobile app — and consumes commerce APIs to render products, prices, and checkout flows.

The practical implication is that you assemble your commerce stack from best-of-breed components rather than accepting whatever the monolith provides. If Algolia is the best search engine for your use case, you use Algolia. If Contentful is the right CMS, you use Contentful. If Elastic Path provides the commerce engine with the pricing and catalogue flexibility you need, you use Elastic Path.

Assessing Migration Readiness

Not every organisation should migrate to MACH architecture tomorrow. The assessment phase is critical and should be rigorous. At McKenna Consultants, we typically evaluate readiness across five dimensions.

1. Business Complexity

MACH architecture delivers the greatest ROI when business requirements are genuinely complex. If you sell a simple catalogue of products through a single website with standard pricing, a monolithic platform may serve you perfectly well. Migration makes sense when you have:

• Multiple sales channels with different presentation requirements
• Complex pricing models (contract pricing, tiered volumes, negotiated rates)
• Authenticated buyer portals with role-based access
• Frequent product catalogue changes that need to go live without a full deployment
• International requirements (multi-currency, multi-language, regional tax rules)

2. Technical Debt

Assess the current state of your monolithic platform. How heavily customised is it? How many integrations depend on its internal data model? How far behind are you on vendor upgrades? Heavy customisation is paradoxically both a reason to migrate (the debt is unsustainable) and a complication (those customisations represent business logic that must be preserved).

3. Team Capability

MACH architecture requires a different skill set than managing a monolithic platform. Your team needs experience with API integration, modern JavaScript frameworks, CI/CD pipelines, and cloud infrastructure. If your current team is primarily configured around the monolith’s admin interface, you will need to invest in upskilling or augment with specialist partners.

4. Integration Landscape

Map every system that currently integrates with your commerce platform: ERP, PIM, WMS, OMS, CRM, marketing automation, analytics, loyalty, payments. Each integration must be redesigned for the new architecture. This is often the most underestimated workstream.

5. Stakeholder Alignment

Migration is a strategic investment, not a technical upgrade. It requires commitment from the C-suite, realistic timelines, and clear success metrics. If the business expects to “replatform over a weekend,” the project will fail.

The Phased Migration Approach

The single biggest mistake organisations make with MACH architecture migration planning is attempting a big-bang cutover. The monolithic platform is decommissioned on a Friday; the new composable stack goes live on a Monday. This approach maximises risk and almost always results in delayed launches, budget overruns, and damaged customer experience.

The alternative is a phased migration that progressively moves capabilities from the monolith to composable services while keeping the existing platform operational throughout.

Phase 1: Decouple the Frontend (Weeks 1-8)

The lowest-risk starting point is headless. Place a new frontend application in front of your existing monolithic platform, consuming its APIs (or building a thin API layer if the monolith does not expose one). The customer experience improves immediately — faster page loads, better mobile performance, modern UX — while the backend remains unchanged.

This phase delivers visible results quickly, builds team confidence with the new architecture, and creates the API abstraction layer that subsequent phases depend on.

Phase 2: Extract Search and Content (Weeks 6-14)

Move search to a specialist service (Algolia, Elasticsearch, Elastic Path’s native search) and content management to a headless CMS. These are read-heavy, customer-facing capabilities where the performance improvement is immediately measurable. The monolith’s product data feeds the new search index; content authors work in the new CMS.

Phase 3: Migrate the Commerce Engine (Weeks 12-24)

This is the core migration: moving product catalogue, pricing, cart, and checkout to the new commerce engine. At McKenna Consultants, we typically implement this using Elastic Path, whose API-first architecture handles complex B2B pricing models, multi-currency support, and custom product configurations natively.

Data migration is the critical path here. Product data, customer accounts, order history, and pricing rules must be migrated with full fidelity. We cover data migration strategy in detail below.

Phase 4: Reconnect Integrations (Weeks 18-30)

Rebuild the integration layer connecting the new commerce engine to ERP, WMS, OMS, and other back-office systems. Event-driven architectures using message queues (Azure Service Bus, AWS SQS, RabbitMQ) provide more resilient integrations than the synchronous point-to-point connections typical of monolithic platforms.

Phase 5: Decommission the Monolith (Weeks 26-36)

Once all traffic is flowing through the new stack and integrations are stable, decommission the monolithic platform. This is the phase where you stop paying the legacy licence fees and hosting costs.

The exact timeline depends on the complexity of your implementation. A straightforward B2C migration might compress into 16-20 weeks. A complex B2B implementation with multiple buyer portals and deep ERP integration could extend to 9-12 months.

Data Migration Strategy

Data migration is where MACH architecture migration projects succeed or fail. The approach must be methodical.

Product Data

Export your complete product catalogue including attributes, variants, pricing tiers, images, and relationships. Map every field to its equivalent in the new commerce engine. Identify gaps where the new platform models data differently. Build automated migration scripts that can be run repeatedly during the transition period — you will need to keep the product catalogue synchronised between old and new systems until cutover.

Customer Accounts

Customer accounts, saved addresses, payment methods, and authentication credentials must migrate cleanly. Consider whether this is also the right moment to consolidate customer data from multiple sources into a single customer data platform.

Order History

Historical orders may not need to migrate into the new commerce engine at all. Many organisations keep order history in the ERP or a dedicated data warehouse and build read-only interfaces for customer self-service. This avoids the complexity of mapping legacy order data models to the new platform.

Pricing and Promotions

This is often the most complex data migration workstream, particularly for B2B organisations with thousands of customer-specific price lists, volume discount matrices, and negotiated contract rates. Document every pricing rule in the legacy system before attempting to recreate it in the new engine.

Team Restructuring

A composable architecture changes how your team works. The monolithic model typically has a “platform team” that manages everything. The composable model distributes ownership across specialist teams.

Frontend team. Owns the customer experience across all channels. Works with modern JavaScript frameworks, consumes commerce APIs, and can deploy independently.

Commerce/API team. Owns the commerce engine configuration, pricing rules, and catalogue management. Works closely with the business to translate commercial requirements into platform configuration.

Integration team. Owns the middleware layer connecting commerce to back-office systems. Expertise in event-driven architecture, API design, and data transformation.

DevOps/Platform team. Owns the cloud infrastructure, CI/CD pipelines, monitoring, and observability. Ensures all services are deployed, scaled, and monitored correctly.

This restructuring does not necessarily mean hiring more people. It means reorganising existing capabilities and filling specific skill gaps — often with a specialist partner like McKenna Consultants providing the composable commerce and integration expertise while internal teams focus on business logic and customer experience.

Building the Business Case

Migration requires investment, and the business case must be compelling. The strongest arguments are:

Revenue Impact

Brands that migrate to composable architecture typically see 15-30% improvements in conversion rates, driven by faster page loads, better mobile experiences, and the ability to A/B test and personalise at speed. For a brand doing GBP 10 million in annual online revenue, a 20% conversion improvement represents GBP 2 million in additional revenue.

Total Cost of Ownership

Monolithic platform licence fees escalate year on year. Hosting costs for on-premises or single-tenant deployments are significantly higher than cloud-native alternatives. Custom development on the monolith costs more per feature because of the regression testing burden. Build a five-year TCO comparison that accounts for licence fees, hosting, development velocity, and maintenance costs.

Speed to Market

The ability to deploy changes to individual services without full-stack regression testing transforms your release cadence. Teams that were deploying monthly on the monolith deploy daily or weekly on a composable stack. In competitive markets, this velocity advantage compounds over time.

Strategic Flexibility

Composable architecture eliminates vendor lock-in. If a better search engine emerges, you can swap it in without rebuilding your checkout. If your commerce engine vendor raises prices or stagnates on innovation, you can migrate that component without replacing everything else. This optionality has real financial value.

Common Pitfalls to Avoid

Having guided multiple organisations through this process, McKenna Consultants has observed several recurring pitfalls.

Underestimating integration complexity. The commerce engine migration is visible and gets the attention. The 15 integrations that need to be rebuilt are less glamorous but consume more effort. Budget accordingly.

Choosing too many vendors. The composable approach lets you pick best-of-breed for every capability. That does not mean you should. Every additional vendor adds integration complexity, contract management overhead, and potential points of failure. Start with a focused stack and expand deliberately.

Neglecting content migration. Product descriptions, category pages, landing pages, and promotional content all need to move to the new CMS. This content migration is labour-intensive and is frequently left to the last minute.

Skipping the parallel running period. Run the old and new systems in parallel for at least 4-6 weeks before decommissioning the monolith. This gives you a fallback if issues emerge post-migration and lets you validate data consistency.

Next Steps

If you are evaluating a move from monolithic commerce to MACH architecture, the first step is a structured assessment of your current platform, business requirements, integration landscape, and team capabilities. That assessment should produce a clear recommendation — migrate, stay, or take an incremental approach — with a phased plan and realistic timeline.

McKenna Consultants provides headless commerce migration consultancy for UK and international organisations. As an Elastic Path implementation partner, we bring deep experience in composable commerce architecture, API integration, and the phased migration approach described in this guide. If you are ready to explore what MACH architecture could mean for your business, we would welcome the conversation.