Custom apps, Shopify Flow and Functions
Custom Shopify app and automation development
OUXP builds custom Shopify apps and automations for brands whose team repeats the same manual work every day, or whose store needs rules no app provides. We check Shopify’s own features, Shopify Flow and maintained apps first, and build only what they can’t do. The routine work then runs on its own, your team handles only the exceptions, and you own the code – with its running costs agreed before work starts.
When apps and admin screens stop fitting the way you work
Six situations bring most merchants to us for app or automation work. Each one has a different answer – and not all of them need code.
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The same manual job, every day
- What you see
- Someone tags orders, copies stock numbers or exports a report by hand – and mistakes slip in on busy days.
- What we build
- A Shopify Flow workflow or a small app that does the job when the event happens, and passes only the real exceptions to a person.
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An app almost fits
- What you see
- An app covers most of the workflow, and your team works around the rest with spreadsheets and notes.
- What we build
- A custom app for the part that is specific to your business, connected to the apps that already work.
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Rules Shopify doesn’t ship with
- What you see
- You want discounts, shipping options, payment methods or cart limits that follow your own rules – or your store relied on Shopify Scripts, which stopped running on June 30, 2026.
- What we build
- The logic as Shopify Functions inside a custom app (Shopify Plus), tested against realistic carts before it goes live. On other plans, an App Store app that uses Functions often covers it.
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Systems that don’t agree
- What you see
- Orders, stock and customer records drift apart between Shopify, your ERP, 3PL and CRM.
- What we build
- A connection with one agreed source for each record, safe retries and failure alerts – so nobody retypes orders into a second system and stock counts stay accurate. It is the core of our commerce integrations work.
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Decisions made from spreadsheets
- What you see
- Every Monday someone stitches a report together from exports, and it is out of date by Tuesday.
- What we build
- A scheduled report or an internal dashboard that reads Shopify and your other systems directly.
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Admin screens built for one item at a time
- What you see
- Wholesale approvals, bulk product edits and price changes run through email and screens that handle one item at a time.
- What we build
- An admin tool inside Shopify – an embedded app page, or an action on the order or product screen – that lets your team approve, edit or reprice many items in one pass.
Also in scope
- Public apps for the Shopify App Store, built to pass Shopify’s app review
- Inventory management and forecasting tools – stock across locations, reorder suggestions from sales history and purchase orders raised for approval
- Returns processing, vendor notifications and warehouse handoffs run by rule instead of by hand
- Pricing engines and customer service workspaces, built as embedded apps in your Shopify admin
- B2B workflows: company approvals, catalog assignment and payment terms
- Checkout and customer account UI extensions – including customer dashboards in the account area
- Theme app extensions instead of edits to your theme’s code, placed and configured in the theme editor
- App features for Hydrogen or Next.js storefronts – see headless commerce
- Catalog-wide imports and exports with Shopify’s bulk operations
- Fixes and takeovers of apps another developer built
Industries we build for
Apps and automations for fashion and apparel, beauty and cosmetics, health and wellness, food and beverage, manufacturing and B2B commerce brands. Our industries page shows where each kind of store breaks on Shopify and what we build for it.
Do you need a custom app at all?
Often not. We work up this ladder and stop at the first step that does the job, because every step up adds code or fees that someone has to carry for years.
| Option | Fits when | What you carry | Typical example |
|---|---|---|---|
| 1. Shopify’s built-in features | Shopify already solves the need: discounts, markets, metafields, B2B catalogs and payment terms | Nothing extra – it is part of your plan, configured well | Volume pricing for wholesale buyers through a B2B catalog |
| 2. Shopify Flow | A store event or a schedule should start a predictable rule: tag, route, hold, notify, update | Workflows to document and watch – Flow itself is free and needs no hosting | Hold fulfillment and alert the team when an order is flagged as high risk |
| 3. A maintained app | A public app does what you need, its vendor keeps it updated and the price is known | A monthly fee, the vendor’s roadmap and any script weight it adds to your storefront | Subscriptions, reviews or bundles from an established App Store app |
| 4. A custom app or integration | The need is specific to your business and the value is clear: your rules, your systems, your volume | Code, hosting and Shopify API updates – owned by you, maintained by us or your team | Discount rules in Shopify Functions (needs Shopify Plus), or an order sync with your ERP |
Steps can combine: a custom app can feed a Flow workflow, and a maintained app can sit next to a small custom one. Apps already slowing the storefront? See performance optimization.
Honest note
Predictable tasks often need no AI at all. Tagging orders, routing requests or flagging low stock are rules – they run faster, cost less and fail more visibly than a model. We add an AI step only where a task needs interpretation, such as drafting product copy from supplier data, with a person reviewing the result (more on our AI commerce solutions page).
What merchants say about our app work
When code is the answer: a central inventory system for a custom setup, a custom app that turned into a year of ongoing work and a Recharge checkout conversion – quoted word for word from the Shopify Partner Directory.
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“Others told us it wasn't possible but Vitali created a central inventory system that works with our custom setup. Great work and communication.”
Dive Bar Shirt Clubvia Shopify Partner Directory (external site)Apps & integrations -
“We have now been working together for 1 whole year, and will continue to do so. Highly recommended.”
Restokit via Shopify Partner Directory (external site) Apps & integrations About this project
A custom app build, followed by a year of ongoing work together.
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“Implemented a recharge shopify checkout conversion and I could not be happier with how smooth everything went with Vitali.”
FANGORIAvia Shopify Partner Directory (external site)Apps & integrations
Reviews sometimes name our engineers – everyone named is part of the OUXP team.
What Shopify Flow can automate – and where it stops
Shopify Flow is Shopify’s free automation app on the Basic, Grow, Advanced and Plus plans. A workflow starts from a trigger – an order created, stock changed, a customer tagged, a set time – checks conditions and runs actions. We set it up and document it before suggesting code.
Typical Flow workflows
- Tag and route orders by value, channel, region or B2B company
- Hold fulfillment and alert the team when an order’s risk is high
- Tell purchasing when a variant drops below its reorder point
- Tag customers by spend or order count for marketing and service
- Unpublish sold-out products and publish them again on restock
- Scheduled checks, such as a daily list of orders still unfulfilled
When a custom app is the better tool
- The logic needs data from several systems, or must keep its own records
- Calls to another system must queue, retry and reconcile – not fire once and hope
- Your team needs a screen to review, approve or correct work
- The volume or the calculation is more than a workflow should carry
- The rule belongs in the cart or checkout – that is Shopify Functions
Plan details: the Send HTTP request action needs the Grow plan or above, and Flow can use tasks from custom apps only on Shopify Plus – so on Plus, a custom app can add its own triggers and actions for your team to use in Flow.
Custom app or public app – which kind of Shopify app do you need?
Shopify distributes apps in two ways, and the choice can’t be changed once the app is set up. Most merchants who want their own logic need a custom app; a public app makes sense when you plan to offer it to other merchants.
| Question | Custom app | Public app |
|---|---|---|
| Who can install it | Your store, or several stores in the same Shopify Plus organization | Any merchant, from the Shopify App Store |
| Shopify review | Not required | Required before the app is listed |
| Billing merchants | Not through Shopify’s app billing – it is your own tool | Through Shopify’s app billing |
| Shopify Functions (discount, shipping and payment logic) | Only on Shopify Plus stores | On any plan |
| Running it | You own it; we maintain it on a retainer, or hand it to your team | A product: merchant support, updates and Shopify’s App Store requirements |
Private apps no longer exist: Shopify converted them to custom apps in January 2023. Since January 1, 2026, new custom apps are created in Shopify’s Dev Dashboard; ones created in the store admin before then keep working. Platform facts as of October 2026.
What we build with
- GraphQL Admin API
- Storefront API
- Webhooks
- Bulk operations
- Shopify Functions
- Checkout UI extensions
- Customer account UI extensions
- Admin UI extensions
- Theme app extensions
- Shopify Flow
- Shopify CLI
- Node.js
- TypeScript
- React
- Next.js
- Hydrogen
- AWS
- Cloudflare
What happens when an automation gets it wrong?
Five risks come with any app or workflow that changes live store data. Each has a fixed answer in how we build.
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A rule changes prices, stock or orders nobody meant it to
How we handle it
We agree up front which changes a person signs off – bulk edits, price and stock changes, customer messages. Every change the app makes is logged with what changed, when and why, with an agreed way to reverse it. New workflows run on a development store first, then on the live store with a limited scope.
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Shopify events get missed, arrive twice or out of order
How we handle it
Shopify doesn’t promise that every webhook arrives, or arrives in order, so we don’t rely on webhooks alone. Our handlers skip duplicates by webhook ID and sort events by their timestamps, and a scheduled reconciliation job re-reads Shopify data – so a missed event is caught instead of silently lost.
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The data is missing or doesn’t fit the rule
How we handle it
The workflow stops and asks, leaves the field empty or uses an agreed default – it doesn’t guess. Cases the rules don’t cover go to a named owner on your team, and alerts fire when they start to pile up.
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Shopify changes its API
How we handle it
Shopify releases a new API version every 3 months and supports each one for at least 12 months. We build on the GraphQL Admin API, pin each app to a version and schedule the update as routine maintenance before that version is retired – so a version change is planned work, not a surprise in production.
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The app outlives the person who built it
How we handle it
You own the code and the data. Every app ships with documentation of what each part does, where it runs and how to deploy it, so our team, your developers or another agency can pick it up later.
How an app or automation project runs
Six steps from a task done by hand to one that runs on its own. Price, timeline and running costs are set in writing before any code is written.
- 1
Map the task
How the work runs today, step by step, and how long it takes – so the saving can be measured later.
- 2
Choose the approach
A written recommendation: a built-in feature, Flow, an existing app or custom code, with what each costs to run.
- 3
Quote and agree
Build price and timeline in writing, with the four points below agreed before work starts.
- 4
Build and test
On a development store, against realistic orders and the edge cases from step 1 – checking functionality, security, performance and the screens your team uses. Senior engineers use AI tools where they save time, and a senior engineer reviews every change.
- 5
Pilot on the live store
A limited scope for a set period, with every output reviewed. Then expand, adjust or stop.
- 6
Hand over and maintain
Documentation, monitoring, failure alerts and security updates. Ongoing changes can roll into a monthly retainer.
What we map
- Inputs – where the data comes from and in what shape
- Decisions – the rules a person applies today
- Exceptions – the cases those rules don’t cover
- Owner – who is responsible for the result
What we agree up front
- Ownership of the code and the data
- Hosting – where the app runs, who holds the credentials, and how development and live are kept apart
- Support and updates – who watches for errors and who handles Shopify API versions
- Recurring costs – hosting, app fees and maintenance time, estimated per month
Connecting Shopify to the rest of your stack
Many automations end in another system – an ERP, CRM, PIM, OMS or WMS, an accounting, shipping or marketing platform, or a marketplace. We connect them through APIs, webhooks or middleware, check each system’s API and access before promising a connection, and settle four questions with you before building.
Four questions for every connection
- Where does each record originate?
- How, and how often, do updates move?
- What happens when the connection fails?
- Who resolves the exceptions?
Systems we connect Shopify to
- ERP – NetSuite, SAP, Microsoft Dynamics, Acumatica
- CRM – Salesforce, HubSpot
- Marketing – Klaviyo, Attentive, Mailchimp
- Payments – Stripe, PayPal, Adyen, Authorize.net
- Shipping and fulfillment – ShipStation, EasyPost, ShipBob, Flexport
- Marketplaces – Amazon, Walmart, eBay
Emergency support
Store down? Checkout broken?
- Store down or showing errors
- Checkout or payment failures
- A theme or app update broke something
- ERP, inventory or fulfillment sync stopped
Commerce engineers, not a help desk. Every request gets a first response within 30–60 minutes during business hours. Retainer clients with the 24/7 emergency add-on are covered around the clock. Not a client yet? Call anyway.
+1 (818) 651-3226 Emergency line 24/7 · Business hours Mon–Fri, 9 AM–9 PM ET
App and automation questions
Something else? Ask an engineer – first response within 30–60 minutes during business hours (Mon–Fri, 9 AM–9 PM ET).
How much does custom Shopify app development cost?
It depends on four things: how many systems the app touches, whether your team needs its own screens, the data volume, and whether the app must pass App Store review. The first 30-minute call is free; OUXP then quotes in writing and lists the monthly running cost – hosting, fees and maintenance – next to the build price. A Flow workflow usually costs far less than code, so we check that first. Upkeep runs on a monthly retainer from $2,500/month, or from $5,000/month when the app syncs an ERP, CRM or 3PL.
What is the difference between a private, custom and public Shopify app?
“Private app” is the old name: Shopify stopped new private apps in 2022 and converted the rest to custom apps in January 2023. Today a custom app is built for one store, or several stores in the same Shopify Plus organization, and needs no App Store review. A public app is listed on the Shopify App Store for any merchant, passes Shopify’s review and can bill through Shopify. Merchants who want their own logic usually need a custom app.
Do we need Shopify Plus for a custom app?
Not for most apps – custom apps and Shopify Flow work from the Basic plan up. Plus is needed when a custom app contains Shopify Functions (discount, shipping or payment logic), for checkout UI extensions on the information, shipping and payment steps, and for Flow tasks from custom apps. As of October 2026, Plus also gives each app 1,000 GraphQL Admin API cost points per second on a store, against 100 on Basic and Grow and 200 on Advanced – which matters for large catalogs and order volumes.
Can Shopify Flow replace a custom app?
For many tasks, yes. Flow is free on the Basic, Grow, Advanced and Plus plans and handles event-driven rules well: tag, route, hold, notify, update. It is the wrong tool when the logic needs its own stored data, calls to other systems that must retry and reconcile, a screen for your team to approve work, or checkout logic, which belongs in Shopify Functions. Often the answer is both – on Plus, a custom app can add its own triggers and actions to Flow.
Who owns a custom app you build for us?
You do – the code and the data. Ownership is settled in writing before work starts, together with where the app is hosted and who holds the credentials. At handover you get documentation of each part, where it runs and how to deploy it, so the app doesn’t depend on whoever built it.
What happens to a custom app when Shopify updates its API?
Shopify releases a new API version every 3 months and supports each one for at least 12 months. When a version is retired, requests fall forward to the oldest supported version, which can change how an app behaves. We pin each app to a version, test it against new releases and schedule the update as routine maintenance – on a retainer, or quoted as a one-off task. Our apps use the GraphQL Admin API, since REST has been legacy since October 2024.
Can you take over an app another developer built?
Yes. We start by reading the code, the hosting setup and the API version it targets, then tell you what is sound, what needs fixing and what it costs to keep running. Common problems we look for: missing error handling, webhook handlers that drop or double-process events, and an API version close to retirement. We document what we find, so whoever works on the app next starts from written notes.
Can you build AI into a Shopify app or workflow?
Yes, where a task needs interpretation – drafting product descriptions from supplier data, sorting support emails, summarizing order exceptions or turning order data into business insights – always with a person reviewing the output before it reaches the store or a customer. We build these with OpenAI and Anthropic’s Claude models, vector search over your catalog and AI agents inside automation pipelines. For predictable rules we use plain automation, which is cheaper and easier to audit. Customer-facing AI such as support assistants, AI search, product recommendations and merchandising sits with our AI commerce solutions team.
What task would you like to stop doing by hand?
Describe the task, how often it happens and who handles it today. An engineer replies within 30–60 minutes during business hours with a suggested first step – often a Shopify Flow workflow, sometimes a custom app.