Shopify engineering for operationally complex stores

Your Shopify store has outgrown manual work.

We build the custom apps, checkout extensions and integrations that keep orders, catalogs and shipping running as you grow. Led by an engineer who ran an 8-figure Shopify Plus store for six years, on both sides of the storefront.

Tell us about your store View case studies

Builds that fit your stack
Repeat work, automated
A partner for the long run

Services

Work that themes and plugins can't do.

Custom apps and integrations

OAuth, embedded admin UI, webhooks, billing. Distributor and 3PL APIs, subscription platforms, shipping engines. Deployed, installed, documented, yours.

Admin GraphQL · App Bridge · Webhooks

Checkout and admin extensions

Logic Shopify doesn't ship: split-shipment notices, delivery windows that respect cutoffs, rules by cart, state, or SKU. Functions for discounts and shipping, admin blocks and actions where your team works.

Checkout UI Extensions · Shopify Functions · Admin Extensions

Conversion and performance

Product page, cart and checkout changes driven by analytics and tests, not taste. Core Web Vitals fixed at the theme level, so speed holds after launch.

CRO · A/B testing · Core Web Vitals

Search and AI visibility

Technical SEO, structured data and content architecture, extended to how ChatGPT, Perplexity and Google AI Overviews read and cite your catalog.

SEO · GEO · AEO · Structured data

Works with Shopify PlusCheckout ExtensibilityShopify FunctionsAdmin GraphQLLiquidRechargeKlaviyoShipStationPostgresNext.jsFastAPIn8nCloud Run

Proof

Case study: one Plus operation, six systems.

Six years inside one 8-figure store. Architecture and outcomes, not employer names. Measurement windows noted on every number.

01 · Dropship order automation

Every order placed by API. None by hand.

Webhook intake, validation, cheaper-supplier routing, automated placement through two distributor APIs, tracking synced back. Every failure has a state and a queue.

Next.js · TypeScript · Postgres · Shopify Admin API · OAuth2 supplier APIs Read the case study →

2.5xfaster median fulfillment, 3-month window before and after

4% → 41%Shipped same or next day

54% → 23%Shipped after 3 days

02 · Checkout extension + live rate engine

Shipping rates that pay for themselves.

Mixed-cart detection at checkout, live rates from a hosted engine (7 zones), per-order shipping P&L in an embedded admin.

15 to 20%Shipping margin after launch, from break-even

FlatCheckout conversion, monitored at checkout level

Checkout UI Extensions · Carrier Service API · App Bridge · FastAPI · Postgres Read the case study →

03 · Subscription retention systems

Out of stock shouldn't mean cancelled.

Stock-rescue swaps before a charge fails, vector-ranked replacements for discontinued SKUs, human approval on every match. Recurring revenue rescued instead of cancelled.

77%of failed subscription charges traced to one fixable cause

4xCancellation save rate, 6% → 24%, annual average

Swap or switchThe customer decides

Next.js · Postgres + vector embeddings · Recharge API · Klaviyo Read the case study →

04 · GEO and AI-search program

From zero to 300,000+ search impressions.

Technical SEO and structured data first, then a content architecture built for how ChatGPT, Perplexity and Google AI Overviews read a catalog. 300,000+ search impressions in six months, six pages in the top 10, and six pages cited in Google AI Overviews, one of them named by title inside the answer.

Technical SEO · Structured data · Search Console · Content architecture

300,000+search impressions in six months

6 pagesRanking top 10

6 pagesCited in Google AI Overviews

#1Cited source 16 days after the first page published

#6Top page by impressions, of ~17,700 URLs sitewide

Rebuilt live. Store conversion doubled.

Full theme rebuild during a rebrand. No downtime, no traffic drop, structured metafields so merchandising never waits on a developer. Store-wide conversion rate 2x across the 2022 rebuild.

Liquid · JavaScript · metaobjects · Core Web Vitals

06 · 70,000-SKU listing pipeline

Listing and pricing on autopilot. Dropship revenue 6x.

Two feeds normalized, matched and deduplicated before anything is written. Listings created with images, variants and metafields correct, verified against source, repriced against the market. Dropship revenue 6x in 12 months, zero manual listings.

Node.js · Python · Postgres · Shopify Admin API · n8n · Cloud Run

Engagements

Scoped first, shipped behind switches, yours to keep.

1Technical assessment

We review the store, its integrations and the manual work around them. You get a written plan: priorities, risks, what to build first and an estimate for it.

2Defined build

A scoped project, fixed price or hourly, decided after the assessment. Everything ships behind switches, so each piece goes live on its own and can be pulled back without a deploy. Code in your repo, apps on your Partner account, documentation a future developer can read.

3Ongoing support

Support continues after launch: fixes, monitoring and the next items on the list, on terms agreed per project.

Best suited to custom integrations, checkout logic and operational automation.

Stores with several suppliers or warehouses, subscriptions, large or fast-changing catalogs, or shipping rules the checkout can't express. Shopify Plus preferred, not required. No in-house developer needed on your side.

Typical starting points

Supplier and 3PL integrationsCheckout and shipping logicSubscription operationsCatalog pipelinesAdmin tooling

One email is enough to start. We reply within one business day with questions or a plan.

Bart Grudka leads CANDEV from Poland, working with US and EU merchants on US hours. Six years on one Shopify Plus store, from front-end lead to Head of E-commerce. Specialists join per project when the scope calls for it. More at grudka.com and LinkedIn.

Tell us about your store. What's breaking, what's manual, what Shopify won't do. A few lines is enough to start. We reply within one business day with questions or a plan.

we@candev.pl