We are the No. 1
Shopify app development company in the USA.
Forget the overhead of large agencies. Work directly with the senior developers who build your solution. We are a family-run US Shopify app studio specializing in high-performance custom apps, API integrations, and scaling Plus stores with a personal, founder-led approach..
Known from:
Engineering High-Scale Shopify Apps & Custom Store Logic
Bespoke App Engineering
Production-Ready Code
We build high-performance apps and plugins that scale. From initial architecture to passing the rigorous App Store Review, we ensure your SaaS is secure, fast, and “Built for Shopify” certified.
Shopify Plus Extensions
Next-Gen Functions
Break the limits of standard themes with custom Functions and Checkout UI Extensions. We replace slow scripts with native, high-performance logic, ensuring your store remains lightning-fast while adding enterprise-level features.
Direct Founder Access
No Middlemen. US-Based Support.
Work directly with the senior architects who own the codebase. We combine German engineering standards with local US presence to deliver transparent, reliable, and high-ROI development for your brand.
Case studies
The Zero-to-Launch Partnership
From Concept to a Top-Rated Shopify SaaS
App Store Launch • B2B Logic • Shopify Functions • SaaS Architecture
The Challenge: A US founder envisioned a breakthrough B2B wholesale tool but lacked a technical lead. The goal was to engineer a high-performance SaaS that could pass the strict App Store Review and scale to thousands of merchants without latency or security issues.
The Solution: We architected a scalable full-stack solution using Remix and Node.js, prioritizing server-side logic and Functions to ensure content protection without impacting page speed. Our team built a native Shopify Polaris dashboard, providing a seamless, embedded UI/UX for store owners.
The Result: The app achieved the prestigious “Built for” status, the highest mark of quality. Today, it maintains a 4.9-star rating with 900+ reviews, handling massive traffic spikes for thousands of merchants with 99.9% uptime and zero performance lag.
Scaling Europe’s Leading Shipping Platform
Engineering an Enterprise-Level Ecosystem Integration
Carrier API Integration • Logistics Automation • High-Volume Shipping
The Challenge: Sendcloud, Europe’s leading shipping platform, needed a specialized partner to capture this platform’s merchant segment. The goal was to build a native-feel app that seamlessly syncs complex carrier logic with the Shop Admin, ensuring high reliability for thousands of concurrent installs.
The Solution: We engineered a robust API-driven middleware connecting Sendcloud’s core engine with the ecosystem. Utilizing high-performance Webhooks and a Polaris-based dashboard, we automated real-time label creation for 170+ carriers and branded tracking directly within the Shopify environment.
The Result: The integration successfully opened the App store for Sendcloud, achieving a 4.6-star rating with over 400 reviews. It became a go-to solution for thousands of merchants, significantly reducing shipping errors and manual labor while offering enterprise-grade delivery features at scale.
Scaling a High-Growth US Knitting Startup
Custom Product Logic & Bundle Builder
Custom UI/UX • Bundle Logic • Inventory Automation • D2C Growth
The Challenge: A US-based knitting startup needed a solution for complex product configurations. Depending on the size and color of a knitting set, a specific number of wool balls had to be automatically calculated and bundled, requiring a highly flexible backend and a seamless customer experience.
The Solution: We engineered a custom Bundle & Configuration Engine with a tailored UI. This allowed the brand to define individual wool ball requirements per variant. We utilized Shopify’s AJAX API to ensure real-time inventory updates and a fast, intuitive selection process for the end consumer.
The Result: The sophisticated technical solution and seamless UX provided a “proof of concept” that convinced major investors, successfully securing the startup’s next round of funding. The automated system eliminated manual errors, providing a rock-solid foundation for their rapid US market expansion.
and many more...
“Behind every line of code is a commitment to engineering excellence.”
Marvin & Daniel - Your Lead Engineers.
Directly connected to your codebase,
without the agency bloat.
When you work with us, you partner directly with the architects. We are senior engineers and founders who maintain high engineering standards across every single line of code.
No middlemen. No junior developers. We manage and execute your vision from the first diagram to the public App Store launch, ensuring your architecture is Production-Ready and built to scale.
Our services
We turn bold visions into scalable infrastructure. We partner with founders, entrepreneurs, and CTOs to ship production-ready code that drives growth. From complex B2B logic to enterprise integrations, we provide the expertise to transform your Shopify idea into a market-leading product.
Public & Private App Engineering
We build high-performance plugins that scale. From initial architecture to passing the rigorous App Store Review, we ensure your SaaS is secure, fast, and “Built for Shopify” certified.
- Full-stack Remix & Node.js development
- App Store Launch Strategy
- Embedded UI with Polaris
- Scalable AWS & Heroku Infrastructure
- Ongoing Maintenance & Security Updates
Custom Plus Solutions & APIs
Large-scale merchants need more than “off-the-shelf” apps. We bridge the gap between Shopify Plus and your existing tech stack, creating robust, military-grade integrations for complex business logic.
- Custom ERP, CRM & WMS Integrations
- High-Performance API Middleware
- Inventory & Order Sync Automation
- Legacy System Migration
- Webhook Architecture at Scale
Shopify Functions & UX Extensions
Boost your AOV and conversion rates with native ecommerce logic. We replace outdated scripts with lightning-fast Functions and Checkout UI Extensions to customize the buying experience.ecture to passing the rigorous Platform’s App Store Review, we ensure your SaaS is secure, fast, and “Built for” certified.
- Custom Discount & Shipping Engines
- Checkout UI Customizations
- Advanced Product Bundling Logic
- Real-time Cart Validation
- Post-Purchase Offer Engines
Let’s architect your Plugin success story.
Get in touch with our team to learn more and discuss your needs.
Frequently asked questions
Choosing the right technical partner is the most critical decision for your roadmap. We know the stakes are high, and transparency is everything.mattis, pulvinar dapibus leo.
Why should I hire a specialized Shopify App Development Copmany?
Hiring a specialized partner like MILLER+SMITH ensures you leverage the latest Shop-native technologies. We focus on building scalable, high-performance apps that pass the App Store review and utilize the full power of Shopify Plus APIs, giving you a competitive edge over generic software houses.
How much does custom App Development cost?
The cost of custom Shopify development depends on complexity and integration requirements. We provide transparent, project-based pricing following an initial discovery call. By avoiding “agency bloat” and working directly with senior engineers, we deliver enterprise-grade code with maximum efficiency and ROI.
Can you build private apps for Plus merchants?
Yes. We specialize in engineering private apps and custom integrations for Plus stores. Whether it’s complex ERP syncing, custom checkout logic via Functions, or bespoke B2B workflows, we architect secure solutions tailored to your enterprise infrastructure.
What are the benefits of using Functions and Checkout UI Extensions?
Shopify Functions and UI Extensions are the modern standard for customizing the checkout experience without compromising site speed or security. We use these tools to build custom discount engines, shipping logic, and checkout upsells that are fully compatible with the platform’s “Built for Shopify” performance standards.
Do you provide ongoing maintenance for Shopify Apps?
High-scale integrations require proactive maintenance. We offer dedicated support and maintenance packages to ensure your app remains compatible with Shopify’s frequent API updates, remains secure, and continues to perform optimally as your traffic scales.
How do you handle API integrations with ERP, CRM, and WMS systems?
We are experts in architecting robust API middleware. We connect Shopify Plus to external systems like NetSuite, SAP, or custom WMS platforms, ensuring real-time data synchronization for inventory, orders, and customer profiles with zero latency.
What is the typical timeline for a Plugin development project?
A production-ready plugin or complex integration typically takes 4 to 12 weeks. Our agile, sprint-based approach allows us to ship a functional MVP quickly, ensuring you can begin generating revenue while we iterate on advanced features.
Will I own the source code of my micro SaaS solution?
Built for Long- Term Success
The Ecosystems App Store is no longer just a marketplace; it’s a global stage for high-performance commerce tools. At MILLER+SMITH, we help founders identify and seize untapped opportunities within this ecosystem. Our engineering process is designed to turn complex technical challenges into user-friendly, scalable integrations that stand out in a crowded market.
We specialize in navigating the rigorous ‘Built for Shopify’ requirements, ensuring your app meets the highest standards of speed, security, and merchant experience. From architecting private enterprise integrations to launching public SaaS products used by thousands of merchants, we provide the technical foundation to scale your vision.
Working with Marvin & Daniel means more than just hiring developers—it’s about partnering with engineers who understand the mechanics of the Shopify App Store and how to build products that drive real ROI for merchants.
Talk soon,
Marvin & Daniel
Shopify App Development:
Where Strategy Meets a High-Performance Stack
Building a successful intergration is about more than just functionality—it’s about creating a seamless experience that merchants can trust. We don’t just “write code”; we work in focused sprints to hit your milestones and turn complex requirements into scalable e-commerce tools.
Beyond Functionality: Trusted Integrations
Building a successful integration is about more than just features—it’s about creating a seamless experience that merchants can trust. We don’t just “write code”; we work in focused sprints to hit your milestones and turn complex requirements into scalable e-commerce tools.
Our Core Tech Stack for the Ecosystem
To build apps that are fast, secure, and feel native to the host environment, we rely on a specialized selection of technologies: React, Polaris, App Bridge, Node.js, Remix, Ruby on Rails, PHP (Laravel), Python, GraphQL, REST API, Webhooks, PostgreSQL, MySQL, Redis, Prisma, Fly.io, Heroku, Render, Cloudflare Tunnel, and the official CLI.
Frontend & The “Native” Feel
A merchant should never feel like they’ve left their dashboard. We use React to create highly responsive interfaces, styled with Polaris to mirror the official design system. App Bridge is our key to deeply embedding the software, allowing for seamless navigation and native-style modals within the admin interface.
Modern Backend Logic
We stay ahead of the curve by using Node.js and Remix—the framework now championed by the platform’s own engineering teams. This ensures your app is optimized for performance and follows the latest industry best practices. Depending on the project’s complexity, we also leverage Ruby on Rails, PHP, or Python to build robust server-side logic.
Data Efficiency & Real-Time Sync
In e-commerce, every millisecond counts. We utilize GraphQL for precise data fetching and Webhooks to ensure the app reacts instantly to store events like new orders or inventory shifts. Our data architecture relies on PostgreSQL or MySQL, managed with Prisma and accelerated by Redis for high-speed caching.
Scalable Infrastructure
Reliability is non-negotiable. We host our applications on professional-grade platforms like Fly.io, Heroku, or Render. By integrating Cloudflare Tunnel and the platform-specific CLI into our daily workflow, we guarantee a secure environment for testing and a deployment process that just works.
Developing for this specialized marketplace requires a specific set of tools. We’ve mastered the stack so you can focus on growing your business.