Custom Shopify App Development. Built for What Apps Cannot Do.
Devvista is a software development and growth agency that builds custom Shopify apps for stores whose workflow no App Store app covers: syncing with an ERP such as Odoo, applying your own pricing and order rules, and adding logic at checkout. We scope the work in writing first, so you know the build, the hours and what runs where before anything is coded.
When Another App Is Not the Answer
Most Shopify stores start with App Store apps, and that is the right move. The trouble starts when the business grows past them. Orders are copied into a spreadsheet by hand. Wholesale customers need prices no discount app can express. A warehouse system and the store disagree about stock. Three apps are stacked to approximate one workflow, and each charges monthly.
The cause is usually the same: the store holds the data, but the rules live in someone's head or another tool. The fix is software that carries those rules and runs without a person in the middle. That is what custom Shopify app development is for.
Below we set out how to decide whether you need a custom app, what we build, the steps we follow, a worked cost example, and how to tell afterward that it paid off.
Bring a list of the apps you pay for and the manual steps your team repeats. We will tell you which can be replaced, which should stay, and what a custom app would cost.
Request an App ReviewCustom Shopify App or App Store App?
Use this table before you spend anything. We would rather tell you to buy an existing app than build one you do not need.
| Your situation | What we would recommend |
|---|---|
| An existing app does the job at a price you accept | Install it. No custom work. |
| Two or three apps are patched together to do one thing | Replace them with one custom app, once the monthly costs and failure points are added up. |
| Shopify must exchange data with an ERP, warehouse or accounting system | Custom app that syncs inventory, orders and customers, with one system named as the source of truth. |
| Wholesale or B2B pricing and rules that discount apps cannot express | Custom app, and Shopify Functions where the logic must run in checkout. |
| You want to sell the app to other merchants | Public app. This is a different project, with Shopify's approval process and billing. |
Shopify's developer documentation describes two main routes. Public distribution is for apps installed on many stores and needs Shopify's approval. Custom distribution installs on a single store, on several stores in one Plus organization, or on development stores, and needs no approval.
The same documentation says that when you are building for a specific merchant you typically use custom distribution, and that merchants cannot be charged for custom apps through Shopify's app billing. Apps created inside the Shopify admin with a pre-generated access token can no longer be created, though existing ones keep working.
Shopify App Development Services
Six kinds of custom app cover most of what store owners ask us for.
ERP and Odoo Integration
Inventory levels, orders, products and customers moving between Shopify and your ERP, with retries when a call fails and an admin screen that shows what did not sync. As an official Odoo partner, we can also design the Odoo side, so both ends are planned together.
SyncB2B and Wholesale Rules
Customer-specific pricing, minimum quantities and approval steps, built around how you actually sell.
RulesCheckout Logic
Discount types, hidden payment or delivery options, and order checks, using Shopify Functions.
CheckoutOrder Routing and Fulfillment
Rules that send each order to the right warehouse, supplier or carrier, and push tracking numbers back to the customer. Useful when stock sits in more than one place or some items ship direct from a supplier.
RouteAdmin Screens and Reports
A page inside the Shopify admin that shows your team the numbers they now compile by hand, and lets them act on them.
AdminCustom Data and Storefront Features
Extra product or customer data, and storefront features such as quote requests or product configurators, tied to your back office.
ExtendA note on Shopify Functions. Shopify's documentation says Functions let developers customize Shopify's backend logic, with examples including new discount types, hiding a payment option, renaming a delivery option and blocking checkout when an order breaks a rule. The same documentation says only stores on a Shopify Plus plan can use custom apps that contain Function APIs, while public apps containing functions work on any plan. We confirm your plan before designing anything that depends on them.
How a Custom Shopify App Gets Built
The spec comes first. Most app projects go wrong in the first week, when nobody wrote down which system owns which data.
Define the Job
We write the workflow as it runs today, name the manual steps, and decide what the app must do and what it must leave alone. You approve a one-page spec.
Check App Store First
We look for an existing app that covers the spec. If one does, we tell you and stop there. If none does, we move on with the cost and the gaps documented.
Choose Distribution and Hosting
We pick the app type, confirm your Shopify plan, and decide where the backend runs. Shopify hosts extensions and Functions, and the app's own backend is hosted by you, in your account.
Build on a Development Store
We scaffold the app with Shopify CLI, build against Shopify's GraphQL Admin API, and run it on a development store with your data shape, so you can try it before it touches live orders.
Test With Real Cases
We replay your awkward orders: partial refunds, split shipments, out-of-stock items, a customer with special pricing. Failures are logged with a reason, not swallowed.
Launch and Hand Over
We install on the live store, watch the first orders, and hand over the code, hosting access and a short runbook, so you are never dependent on us to keep the lights on.
What Custom Shopify App Development Costs
Devvista quotes either a fixed price from $500 to $100,000 depending on complexity, or hourly work from $10 to $100 an hour depending on the developer.
The price follows the number of systems the app touches, the number of rules it applies, whether data moves one way or both ways, and how much of it needs a screen for your team. Hosting is a separate monthly cost, because Shopify does not host the app's backend.
Worked example (an estimate, not a quote). Assume a custom app that syncs inventory and orders between a Shopify store and an ERP, with an admin screen for failed syncs. Using one illustrative rate of $40 an hour:
| Work | Hours |
|---|---|
| Spec, data mapping and source-of-truth rules | 12 |
| App scaffold, authentication and webhooks | 20 |
| Inventory sync | 30 |
| Order sync | 30 |
| Error handling, retries and the admin screen | 20 |
| Testing with real store data | 20 |
| Deployment and handover | 8 |
| Total | 140 hours, about $5,600 at $40 an hour |
As an estimate, that scope fits three to six weeks of calendar time. If it replaces two apps costing $50 a month each, the saving alone is $1,200 a year, and the larger gain is the staff time no longer spent re-entering orders. Work that out for your own store before you commit. The numbers above are an assumption, not a promise.
How to Know the App Is Paying Off
Pick two or three numbers before the build and measure them after. Good ones are the hours per week your team spent on the manual task, the number of orders needing a manual fix, and the monthly cost of the apps the custom one replaced.
Check the app's failed-sync list weekly for the first month. A short list that shrinks is healthy. A list that grows means a rule was missed, and we fix it as part of the handover period.
Plan for upkeep too. Shopify changes its APIs over time: it describes the REST Admin API as legacy as of October 1, 2024, and has required all new public apps to use only the GraphQL Admin API since April 1, 2025. We build on GraphQL from the start, and offer a maintenance retainer if you want us to watch for changes on your behalf.
Sources: Shopify app distribution, Shopify Functions, Shopify REST Admin API and Shopify app building.
Who Should Hire a Shopify App Developer From Devvista
Custom work is worth it when the workflow is specific and repeated. It is a poor use of money otherwise.
If Shopify needs to talk to an ERP, warehouse tool or accounting system, a custom app is often cheaper over a year than copying data by hand.
Rules that depend on who the customer is or what the order contains are where discount apps run out.
The code and the hosting are in your account, with a handover note, so you can change developers at any time.
We will point you to it. Building something that already exists for a few dollars a month wastes your budget.
Building a product for the App Store is a larger project with its own approval process. We can scope it separately, but it is not what this page describes.
Straight
Answers.
The questions store owners ask before they commission a custom Shopify app.
Tell Us About Your Workflow.
Describe the workflow your team repeats by hand and the systems involved. We will tell you whether an app already covers it, and what a custom one would take.
- Written spec before code
- Fixed-price or hourly estimates
- Reply within 24 hours
- Book a call30 minutes, no pitch. Tell us what you want to build.
- Get a straight answerHonest feedback on fit, scope and timeline.
- Decide with no pressureMove ahead only if it feels right. No commitment required.