Shopify Plus Custom App & Checkout Development

We build private applications and checkout modifications for enterprise brands that have hit the native functional limits of Shopify Plus. If generic public marketplace apps degrade your page speed or fail to support your corporate financial workflows, our engineers build dedicated infrastructure to run your custom logic. We replace third-party subscription apps with proprietary code that belongs entirely to your business.

Łukasz Białonoga

CEO of Hmmh Poland

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We build private Shopify applications and secure checkout architectures connected to internal ERP systems like SAP. Our team steps in when generic marketplace plugins conflict, degrade page speed, or fail to support your specific wholesale rules. By combining Polish development agility with the strict data security standards of hmmh Germany, we create backend features that automate your workflows, minimize your total cost of ownership, and directly protect your margin.

Marketing Scalability and Automation in 6 Weeks for Delica (CoffeeB)

E-commerce / Shopware

Marketing Scalability and Automation in 6 Weeks for Delica (CoffeeB)

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Shopware 6 with Baselinker and ERP Optima integrations for Bazar Pupila

E-commerce / Shopware

Shopware 6 with Baselinker and ERP Optima integrations for Bazar Pupila

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Hmmh Poland’s work has yielded significant outcomes in the client’s E‑commerce. Thanks to the team’s diligent efforts, the client has enhanced their site’s performance and elevated their visibility on search engines. The team understands the client’s business requirements.

Marcin Wysocki

Head of Digital, YOPE

Commerce engineering that pays back

Eliminating public app dependency

When your store relies on many different public apps, your system stability is at risk. Heavy public applications inject messy tracking scripts that slow down mobile shoppers and create security loopholes. We build consolidated private applications that run on dedicated server infrastructure. Your store stays fast, clean, and safe from unexpected third-party service outages.

Custom checkout modifications

Standard checkout structures often limit how you interact with business buyers in specific regions. We use Shopify UI Extensions and Shopify Functions to inject custom business logic directly into the purchase flow. Whether you need real-time tax code validation for Central Europe or specific freight shipping calculations based on warehouse availability, we build it directly into the interface.

Rescuing broken app architectures

We frequently take over store implementations that have stalled due to app conflicts or unmaintainable custom code. Our engineering team runs a swift technical audit to locate memory leaks and API bottlenecks. We isolate the broken scripts, clean up the codebase, and deliver a clear development roadmap to restore platform stability.

DACH compliance extensions

Selling to business clients in Germany, Austria, or Switzerland requires compliance with precise consumer display laws and specialized accounting rules. We work with the market experts at hmmh Germany to build custom application layers that automate local invoicing workflows. Your checkout complies with strict regional standards without adding manual administrative tasks for your team.

Are Shopify Plus custom apps right for your operational scale?

Custom applications are an investment for organizations generating 20-100M PLN in revenue that require absolute control over their business logic. We recommend this approach to companies that want to replace unpredictable subscription fees with a stable technical architecture.

For e-commerce managers aiming to optimize conversion rates by removing external scripts that slow down the purchase journey.

For finance departments that require direct invoice synchronization with SAP systems without intermediate plugins.

For wholesale distributors that must process intricate volume discount tables without cart loading delays.

For brands expanding internationally that require custom integrations with local couriers or warehouse systems in the DACH region.

Frequently Asked Questions

Why should an enterprise store choose a private custom app over a public app?

Public apps are built for mass deployment and contain generic code that slows down your storefront. A private custom app is written specifically for your database infrastructure, eliminating conflicts and performance drops. Furthermore, custom apps eliminate monthly subscription costs, giving you complete ownership of your technology stack.

What is the difference between legacy checkout customizations and new Shopify Plus checkout extensions?

Shopify has deprecated old checkout files in favor of Checkout Extensibility using Shopify UI Extensions and Functions. This updated architecture allows us to inject custom business rules and logic safely. Your checkout remains upgradeable, matches your design system perfectly, and scales without risk during peak traffic moments.

How do you approach a project where existing custom apps are causing errors?

We begin with a brief technical audit to find the specific failure points in your API calls or database webhooks. Our engineers stabilize the live environment first to protect your current sales. Once the platform is secure, we deliver a step-by-step roadmap to rewrite or replace the faulty components.

Can custom apps connect Shopify Plus to older, non-standard ERP systems?

Yes. We specialize in building secure middleware applications that translate data between Shopify’s modern GraphQL APIs and legacy enterprise systems. This allows you to automate product synchronization and order routing without forcing your organization to completely replace your core internal ERP database.

Let's talk about your project!

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Łukasz will be your first contact