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 Shopify 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 Shopify apps that scale. From initial architecture to passing the rigorous Shopify App Store Review, we ensure your SaaS is secure, fast, and “Built for Shopify” certified.
Shopify Plus Extensions
Next-Gen Shopify Functions
Shopify Plus Extensions
Next-Gen Shopify Functions
Break the limits of standard themes with custom Shopify 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.
Case studies
The Zero-to-Launch Partnership
From Concept to a Top-Rated Shopify SaaS
Shopify 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 Shopify SaaS that could pass the strict Shopify 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 Shopify 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 Shopify” 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 Shopify Integration
Carrier API Integration • Logistics Automation • High-Volume Shipping
The Challenge: Sendcloud, Europe’s leading shipping platform, needed a specialized partner to capture the Shopify merchant segment. The goal was to build a native-feel app that seamlessly syncs complex carrier logic with the Shopify Admin, ensuring high reliability for thousands of concurrent installs.
The Solution: We engineered a robust API-driven middleware connecting Sendcloud’s core engine with Shopify’s 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 Shopify market 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 Shopify apps that scale. From initial architecture to passing the rigorous Shopify App Store Review, we ensure your SaaS is secure, fast, and “Built for Shopify” certified.
- Full-stack Remix & Node.js development
- Shopify App Store Launch Strategy
- Embedded UI with Shopify 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 Shopify logic. We replace outdated scripts with lightning-fast Shopify Functions and Checkout UI Extensions to customize the buying experience.ecture to passing the rigorous Shopify App Store Review, we ensure your SaaS is secure, fast, and “Built for Shopify” certified.
- Custom Discount & Shipping Engines
- Checkout UI Customizations
- Advanced Product Bundling Logic
- Real-time Cart Validation
- Post-Purchase Offer Engines
Let’s architect your Shopify 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?
How much does custom Shopify 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 Shopify apps for Shopify Plus merchants?
What are the benefits of using Shopify Functions and Checkout UI Extensions?
Do you provide ongoing maintenance for Shopify Apps?
How do you handle API integrations with ERP, CRM, and WMS systems?
What is the typical timeline for a Shopify App development project?
Will I own the source code of my custom Shopify solution?
Built for Long- Term Success
The Shopify 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 Shopify apps 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.