Shopify developer - custom stores, headless checkout, and app integrations

#Shopify developer for UK and Irish merchants

Shopify is hosted commerce: no PHP server to patch, but a theme, a set of apps and a checkout with firm rules. My work sits in that layer. I keep Liquid readable, make webhook consumers safe against duplicates and stop the checkout from breaking when marketing adds another tag.

You bring the graphic design and the wireframes, as a Figma file or a filled-in template showing which element goes where. I build them into a responsive Online Store 2.0 theme. If your content lives in WordPress, I can keep WordPress for editorial and Shopify for the catalogue, with one source of truth for products.

#What to settle before building a Shopify store

Shopify ties catalogue, locations, markets, taxes, payments and fulfilment together. That works until someone tries to push a wholesaler’s logistics into Liquid. A sound project starts with a written list of markets, currencies, warehouses and returns rules.

For UK shops the usual stack is Shopify Payments (available in the UK and Ireland), PayPal, and a pay-later option such as Klarna or Clearpay, with Royal Mail, Evri or DPD for delivery. Selling across the Irish Sea is a VAT question since Brexit: for low-value goods sent from outside the UK, VAT is charged at the point of sale rather than at import (HMRC guidance). I configure the markets and price display; the classification itself comes from your accountant.

Before adding an app I check whether native sections, metaobjects or Shopify Flow already cover the need. Every app adds JavaScript, scopes and another thing that can break after a theme update.

#What I do on a Shopify project

• Metafields and metaobjects for size charts, spec sheets and compatibility tables, with validated CSV imports.
• Online Store 2.0 sections that merchandisers can configure without touching templates that decide LCP.
• Storefront API operations with cursor pagination and error handling for traffic spikes from campaigns.
• Integrations that move orders to an ERP or warehouse through a queue with logs.
• Checkout rules through Shopify Functions and checkout UI extensions, within what your plan allows.
• Measurement of collection and product templates on the devices that feed CrUX, not only on a desktop.

The theme lives in a Git repository with history, and changes go to a development theme before the live one.

{% schema %}
{
  "name": "Featured collection",
  "tag": "section",
  "class": "section-featured-collection",
  "settings": [
    {
      "type": "collection",
      "id": "collection",
      "label": "Collection"
    },
    {
      "type": "range",
      "id": "products_to_show",
      "min": 2,
      "max": 12,
      "step": 1,
      "default": 4,
      "label": "Products to show"
    }
  ],
  "presets": [{ "name": "Featured collection" }]
}
{% endschema %}

query CollectionProducts($handle: String!, $first: Int!, $after: String) {
  collection(handle: $handle) {
    id
    title
    products(first: $first, after: $after) {
      pageInfo {
        hasNextPage
        endCursor
      }
      edges {
        cursor
        node {
          id
          handle
          title
        }
      }
    }
  }
}

// Pseudocode: Node-style handler; answer within 5 s, do the ERP work in a queue
async function handleOrderCreate(payload, headers) {
  const webhookId = headers["x-shopify-webhook-id"];
  const orderId = payload?.id?.toString();
  if (!webhookId || !orderId) return { status: 400 };

  const dedupeKey = `orders/create:${webhookId}`;
  if (await cache.has(dedupeKey)) {
    return { status: 200, body: "duplicate ignored" };
  }

  await enqueueErpExport(orderId);
  await cache.set(dedupeKey, "1", { ttlSeconds: 86400 });
  return { status: 200 };
}

{% assign cap = section.settings.products_to_show | default: 8 %}
{% assign collection = section.settings.collection %}
<ul class="product-grid" role="list">
  {% for product in collection.products limit: cap %}
    <li>
      <a href="{{ product.url }}">
        {{
          product.featured_image
          | image_url: width: 640
          | image_tag: loading: 'lazy', widths: '320,640,960'
        }}
      </a>
    </li>
  {% endfor %}
</ul>

mutation cartLinesAdd($cartId: ID!, $lines: [CartLineInput!]!) {
  cartLinesAdd(cartId: $cartId, lines: $lines) {
    cart {
      id
      totalQuantity
    }
    userErrors {
      field
      message
    }
  }
}

{
  "cartId": "gid://shopify/Cart/YOUR_CART_ID",
  "lines": [
    {
      "merchandiseId": "gid://shopify/ProductVariant/YOUR_VARIANT_ID",
      "quantity": 1
    }
  ]
}

#Liquid themes and Online Store 2.0

Online Store 2.0 replaced fixed templates with JSON templates built from sections, so merchandisers can rearrange pages in the theme editor. Stores still on older themes usually stay there because their layouts were built inside a page-builder app. I treat the move as a refactor: remove duplicate snippets, cap collection loops and give images fixed aspect ratios so dynamic merchandising does not cause layout shift.

Accessibility is part of the Liquid work: focus handling in the cart drawer, contrast on buttons, and announced stock messages. I work with the Shopify CLI against a development theme and keep the theme in Git, so every change has a history and a way back.

#ERP and warehouse integration through webhooks

Orders often have to reach a central warehouse or a 3PL. Topics such as orders/create and inventory_levels/update need idempotent consumers, because a duplicate delivery or a bad SKU should not create a second pick or freeze a record in the ERP. I put a queue between Shopify and the ERP (Cloudflare Queues or AWS SQS, for example), keep a view of pending and failed events, and add a reconciliation job that compares stock in Shopify with the warehouse.

If you run WooCommerce today, the move can happen in stages: catalogue and payments on Shopify first, the old checkout switched off once webhooks are stable.

#Performance and Core Web Vitals

Shopify serves the storefront from its own network, but the theme and the tags decide the field metrics. INP on phones is usually damaged by mega-menus, product carousels and review widgets loading too early. I profile the templates, defer or remove third-party scripts, and move tags server-side only where your privacy policy allows it.

I do not promise a conversion uplift. You get a measurement protocol and a list of the bottlenecks I removed, with before and after traces on the same throttling profile.

#Migrations without losing search visibility

Moving platforms without a redirect map shows up as a wall of 404s in Search Console. I export old URLs, map each to its new handle with a 301, and check crawl errors after launch. Technical attributes move to metafields so collection filters survive. Product and Organization structured data match what the page actually offers.

#Tools and integrations

If you are building a Shopify app and need help with its App Store listing, onboarding measurement and follow-up, that work is go-to-market engineering.

#Experience and Shopify certificates

I have built websites since 2006. Next to WordPress and WooCommerce work, I have connected WordPress and WooCommerce stores with Shopify for clients in Poland and the UK. My Shopify Partner Academy course certificates, including Liquid Storefronts for Theme Developers and the Conversion Rate Optimization path, are published on Credly; the badges above link to them. These are course certificates, not a Shopify Partner agency status. Recommendations from clients are on LinkedIn and on the about page.

#How to start a Shopify project

Send me your store URL, the list of apps and integrations, and when your busy periods are. You get written questions where something is unclear, then a quote with the scope and the assumptions it rests on.