Custom eCommerce Development for Stores the Apps Cannot Build

Product configurators, custom checkouts, B2B workflows, pricing engines, and integrations, engineered on BigCommerce, Shopify, Magento, WordPress, and headless stacks by developers who own the result.

Every platform ships with a theme, an app store, and a ceiling. Custom eCommerce development is what happens above that ceiling: the feature a plugin almost does, the checkout step your business model needs, the ERP that has to see every order the second it is placed. MAK Digital has written that layer for fifteen years, on every major platform, as part of our web development services. We build it to survive platform updates, to stay fast, and to be maintainable by any competent developer, and we document it so it is yours.

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    MAK Digital at a glance

    • 15

      Years in eCommerce

      Fifteen years of building, migrating, and growing online stores for B2B and B2C brands.

    • 30+

      In-house specialists

      SEO, AI search, paid media, design, and development experts under one roof.

    • USA

      US-led, globally staffed

      A US-based core team you talk to directly, backed by vetted specialists worldwide.

    • 4.9

      Client rating

      Average score across 650+ verified client reviews.

    Custom eCommerce development

    Custom Functionality We Build

    These are the requests that arrive after a merchant has tried three apps. Each is built on your platform's APIs and templating system, so it behaves like part of the platform rather than a bolt-on.

    • Product Configurators & Builders

      Step-by-step builders for made-to-order, bundled, and customizable products: dependent options, live pricing, compatibility rules, previews, and cart line items that carry the configuration through checkout, fulfillment, and the ERP.

    • Custom Checkout Development

      Checkout flows shaped by your business: custom fields and validation, delivery date and installation scheduling, deposits and split payments, terms and financing, age and license verification, and post-purchase steps, using Shopify Checkout Extensibility, BigCommerce checkout SDK, or Magento checkout modules.

    • B2B Pricing, Quotes & Ordering

      Customer-specific price lists, tiered and contract pricing, quote requests and negotiation, quick order and bulk upload, requisition lists, approval chains, net terms, and punchout, on top of B2B platforms or tools such as B2B Ninja.

    • Custom Apps & API Development

      Private and public apps on the BigCommerce API, Shopify Admin, Storefront, and Functions APIs, Magento REST and GraphQL, and the Volusion API, for functionality that has to run inside the platform's admin, storefront, or checkout.

    • ERP, OMS, PIM & Marketplace Integrations

      Bidirectional syncs for orders, inventory, pricing, products, and customers with NetSuite, Dynamics, SAP, Acumatica, QuickBooks, Akeneo, ShipStation, and marketplaces, built as event-driven middleware that survives spikes and retries failures on its own.

    • Subscriptions, Memberships & Loyalty

      Subscription and replenishment models with custom billing rules, membership tiers with gated pricing and content, and loyalty programs with earn and burn logic tied to your margins, built on platform billing APIs or integrated with specialist tools.

    • Custom Search, Filtering & Merchandising

      Faceted navigation for complex attributes (fitment, dimensions, compatibility), year-make-model and part finders, boosted and pinned results, and merchandising rules your team controls without a developer.

    • Custom Theme & Storefront Engineering

      Custom templates, components, and interactions on BigCommerce Stencil, Shopify Liquid and Hydrogen, Magento Hyvä, and WordPress blocks, or a headless storefront when several front ends or a bespoke experience justify it.

    • Automation & Back-Office Tools

      Admin tools, bulk operations, pricing and inventory automations, fraud and compliance rules, reporting dashboards, and workflow integrations that remove manual steps from how your team runs the store.

    Build or install?

    When Custom Development Beats Another App

    Most stores should install before they build; app ecosystems are mature and cheap. Custom development earns its cost in specific situations, and we say which one you are in before we quote. These are the cases where building wins.

    • The App Does 80% and the 20% Is Your Business

      When the missing piece is the pricing rule, the compatibility logic, or the checkout step that makes you different, a custom build is cheaper than working around the gap forever.

    • Three Apps Are Fighting Each Other

      Overlapping apps for bundles, subscriptions, and pricing slow the store and break at the edges. One custom module that does what you need is faster and easier to maintain.

    • The Integration Has to Be Right

      Off-the-shelf connectors map fields their way. When orders, inventory, and pricing must match your ERP exactly, custom middleware with your rules and your error handling is the safe choice.

    • Speed Is the Feature

      App scripts stack up; a custom implementation in the theme loads what the page needs and nothing more, which is often the difference between passing and failing Core Web Vitals.

    • You Need to Own It

      When a capability is central to the business, depending on a third-party app's roadmap and pricing is a risk. Custom code you own removes it.

    • AI Has to Use Your Data

      Search, recommendations, and assistants that reason over your catalog, fitment, or inventory need custom integration; generic AI widgets cannot see what makes your products different.

    How custom code stays healthy

    Our Standards for Custom Development

    The failure mode of custom eCommerce work is code that worked at launch and broke at the next platform update. Every custom feature we deliver is built to these rules so that does not happen:

    • Built on supported, versioned platform APIs and extension points, never on undocumented behavior or core file edits
    • Isolated from the theme where the platform allows (apps, modules, plugins), so theme updates do not overwrite it
    • Version-controlled, code-reviewed, and deployed through staging, with a rollback path for every release
    • Automated tests for pricing, checkout, and integration logic, plus manual QA with real orders before launch
    • Performance budgets enforced: no blocking scripts, deferred loading, and Core Web Vitals verified on mobile
    • Security by default: least-privilege API scopes, secrets managed outside the code, input validation, and logging
    • Error handling and retries designed for integrations, with alerts that reach a person when a sync fails
    • Documentation, architecture notes, and handover so your team or any developer can maintain it
    • Ownership: the code, the app credentials, and the accounts are yours from day one

    Custom Development by Platform

    We build the custom layer on the platforms we are certified on, using each one's native extension points.

    How We Deliver Custom eCommerce Development

    Custom work runs like a product build: a scoped and priced spec, a design system, sprints with working software you can test, a launch with monitoring, and documentation and code handed over at the end.

    • Technical Discovery

      We map the requirement, the data it touches, the platform's extension points, and the apps you already run, then confirm whether custom is the right call and write a technical scope with a fixed price.

    • Solution Design

      Architecture, data model, API usage, and UX for anything customer-facing, reviewed with you before code, with edge cases and failure modes listed up front.

    • Build in Increments

      Development on staging in reviewed increments you can try, with automated tests written alongside the code.

    • Integrate & Test

      Connected to payments, ERP, and the rest of your stack; tested with real products, real orders, and the odd cases that break naive implementations; performance and security checked.

    • Release

      Deployed through your release process with a rollback path, monitored through the first days, with your team trained on anything they operate.

    • Maintain

      Updates when the platform or an integrated system changes, monitoring, and improvements, through an ongoing support plan with the developers who built it.

    Merchants Who Needed More Than an App

    Configurators, checkouts, integrations, and B2B workflows that no plugin covered. Their owners on how the custom work turned out.

    • Webeyecare

      Webeyecare

      “If you're a BigCommerce user, hitting up MAKDigital is a smart move. It's a hive of skilled web designers and coders. Rest assured, they'll deliver what you're looking for.”

    • Trent Taucher

      CEO, Budgetheating.com

      “If I could give 6 stars I would! I have worked with Mary and MAK Digital for many years now. They have performed the Affirm Financing integration on our company website as well as many other custom coding work through the years. Pricing is fair for the level of expertise they provide and they always come through with the project quoted and timelines promised.”

    • PMArmory

      PMArmory

      “Teaming up with MAK is a total thrill! We're over the moon with our brand-new website. Alexis was all ears for our needs and hatched a plan that checked all our boxes. Her communication skills throughout the whole process were simply top-notch.”

    Have a feature no app quite delivers?

    Describe what the store needs to do and the platform it runs on. We will reply with an honest answer on build versus install, a technical approach, and a fixed price if custom is the right call.

    Custom eCommerce Development Questions

    When to build, what it costs, how it survives updates, ownership, performance, and support.

    When does custom development make more sense than an app or plugin?

    When the functionality is central to how you sell and no app matches it, when several apps overlap and slow the store, when an integration must map data exactly to your systems, when speed matters and app scripts are the problem, or when you need to own the capability rather than rent it. If an app does the job well, we will tell you to install it; our development team configures and extends apps every week.

    How much does custom eCommerce development cost?

    A single well-defined feature (a checkout customization, a custom filter, a small integration) typically runs in the mid four to low five figures. Product configurators, B2B ordering systems, and ERP or OMS middleware run from the low-to-mid five figures depending on complexity. Headless storefronts and multi-system programs run higher and are scoped in phases. Every project is quoted as a fixed price after technical discovery.

    How long does a custom feature take to build?

    Defined features take three to six weeks including testing. Configurators, custom checkouts, and integrations take six to twelve. Larger systems are delivered in phases so the first useful piece ships early. You get a dated plan with the scope and working software on staging as it progresses.

    Will custom code break when the platform updates?

    Not when it is built correctly. We build on supported, versioned APIs and the platform's official extension points (apps, modules, plugins, checkout extensions) rather than editing core files or relying on undocumented behavior, and we isolate custom code from the theme wherever the platform allows. Under a support plan we also test against platform release notes before updates reach your store.

    Do we own the code?

    Yes. The code, the app credentials, the repositories, and the accounts are yours, with documentation and architecture notes so your team or any developer can maintain it. We do not lock clients into proprietary frameworks.

    Will custom features slow down the store?

    They usually speed it up, because a custom implementation loads only what the page needs while stacked apps load everything on every page. We set performance budgets on every build and verify Core Web Vitals on mobile before release. Our speed optimization work often starts by replacing app sprawl with lean custom code.

    Can you integrate with our ERP, accounting, or warehouse system?

    Yes. We build bidirectional integrations with NetSuite, Microsoft Dynamics, SAP, Acumatica, QuickBooks, Akeneo, ShipStation, and others, as event-driven middleware with retries, logging, and alerts, so a failed sync is caught and repaired rather than discovered as a missing order.

    Do you build custom checkouts?

    Yes, on the platforms that allow it: Shopify Checkout Extensibility and Functions on Plus, the BigCommerce checkout SDK and custom checkout, Magento checkout modules, and WooCommerce checkout blocks. Custom fields, delivery scheduling, deposits, terms, verification steps, and post-purchase flows are the common requests.

    Can you add AI features that use our own data?

    Yes. Custom search and recommendations that reason over your catalog attributes, fitment data, and inventory, and assistants grounded in your products and policies, integrated through the platform APIs and measured like any other feature. We also structure product data so AI shopping agents can read it, which is increasingly where custom development and UX meet.

    What happens after launch?

    Most clients keep the developers who built the feature on a support plan covering monitoring, updates when the platform or integrated systems change, and improvements. If you prefer to maintain it in-house, we hand over documentation, tests, and the release process.

    Development Resources

    From the eCommerce Experts

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