Build vs buy on Shopify: what to own, what to rent, what to wire together

On 30 June 2026, every Shopify Script stopped running. A Script was a small piece of code, written inside Shopify, that controlled discounts and shipping rules. Stores that had bought their discount logic as a Script had to rebuild it. Stores that had written that logic into a custom app (software built just for that store) kept running. One date settled a years-old argument about building against buying, and it did not settle it the way either camp expected.

Autonomous Technologies builds and runs the systems behind Shopify stores. We work for founders and operators who are accountable for the store after launch. The wrong call here costs you a quarter of engineering time, or an app bill that grows every year. That is why this sits inside our integrations work, which means connecting your store to your other software. Every platform claim below links to the vendor’s own documentation, checked 21 September 2026.

Four layers, not two choices

The old framing was build against buy. On Shopify there are four layers, and picking the wrong one is the expensive mistake.

The platform layer is what Shopify already does. Payments, checkout, tax, accounts, fulfilment records. You do not build these and you do not buy them twice.

The app layer covers work that is the same for thousands of stores. Reviews, email, loyalty, help desk. You rent these. You accept the vendor’s roadmap in exchange for speed.

The custom layer is logic specific to how your business makes money. Your pricing rules. Your wholesale terms. Your routing between warehouses. Nobody sells this, because nobody else needs it.

The wiring layer joins the other three. It moves an order into your accounting system. It tells a warehouse to pick. It is where most stores quietly lose their weekends.

Buying means renting a roadmap, and Shopify put a date on that

Shopify Scripts was the platform’s own customisation tool. Merchants used it for years to write the rules for discounts and shipping. Then Shopify retired it.

The changelog, Shopify’s public list of product updates, is blunt about the two dates. From 15 April 2026, “editing and publishing new Shopify Scripts will no longer be possible”. From 30 June 2026, “all Shopify Scripts will cease to execute entirely”.

Checkout moved on the same principle. Shopify states that “as of August 28, 2025, the additional scripts section in the Checkout settings is view-only”. Non-Plus stores (those not on Shopify’s top-tier Plus plan) have until 26 August 2026 to upgrade their Thank you and Order status pages, the screens a customer sees after paying, per Shopify’s checkout upgrade guide.

That is not an argument against buying. Buying is usually right. It is an argument for knowing that the roadmap is not yours, and for keeping a list of what would break if a vendor gave you ninety days.

Building commodity software is how a small team loses a quarter

The opposite failure is quieter and more common. A team decides to build an internal tool rather than pay a licence.

It works for a month. Then it needs error handling, which means a plan for when something fails. Then retries. Then an audit log, a record of who changed what, because someone changed a price and nobody knows who. Six months later your best developer maintains an internal copy of a tool you could have rented, and nobody enjoys using it.

Code is a liability, not an asset. Every line has to be patched, secured and explained to whoever arrives next. That bill does not appear in the original estimate. Neither does compliance. Building your own authentication, meaning the login system, looks cheap. Then a customer asks for a SOC 2 report, an independent audit showing you protect data properly. Now you are paying an auditor on a schedule you did not plan.

The same trap has a newer shape. If what sets you apart is a thin layer on top of someone else’s AI model, reached through an API (a way for one program to ask another for something), you do not have a product. You have a feature the model’s maker can ship themselves. Rent the reasoning. Own your data and the logic that finds the right information to feed the model.

Shopify’s native layer is the one most stores forget to check first

Before you price an app or a build, check whether the platform already does it.

Shopify Functions “allow developers to customize the backend logic that powers parts of Shopify”. In plain terms, a Function is a small piece of custom code that runs inside Shopify’s own checkout. Functions run inside key purchase flows. Discounts, cart contents, delivery options, payment method availability, fulfilment routing and checkout validation (checks that block bad orders) all have Function APIs, meaning ready-made places for developers to plug code in. This is where Scripts logic went.

Shopify Flow is the automation tool Shopify gives you. It is free on Basic, Grow, Advanced and Plus. A workflow is a trigger (something happens), a condition (a check) and an action (what Flow then does). The limits matter to this decision. The Send HTTP Request action, which lets Flow send data to another system, is restricted to Grow, Advanced and Plus. Custom app tasks from partners, meaning extra steps built by outside developers, are Plus only. Usage limits follow the API rate limits on your plan, the caps on how often programs can call Shopify.

So the honest order of questions is short. Can Flow do it? Can a Function do it? Is there an app whose vendor will maintain it? Only then do you write code.

The wiring layer is where ownership actually gets decided

Between a rigid app and a custom service sits the wiring. This is the middle path, and it is where we do most of our work.

Take a common job. An order comes in, a credit check runs, the customer record updates, and a warehouse gets told to pick. The heavy version is a custom service. It brings a hosting bill, key management (keeping passwords and access keys safe), a logging system (a record of what the service did) and an on-call alert that can wake someone at 03:00. The lighter version is a Flow workflow for the Shopify-side steps. For the parts Flow cannot reach, add a self-hosted workflow runner such as n8n, a tool you run on your own server that chains steps together.

You own the logic. You rent the plumbing. When a vendor changes an endpoint, the address your system uses to reach theirs, you edit one node, a single step in the workflow. You do not have to rebuild and republish a whole service.

Built carefully, that layer just keeps running. One platform we built needed no backend work (changes to its behind-the-scenes code) for 18 months, then for 10 more, between October 2023 and July 2026, while the site stayed live. We wrote up how it was built. The detail for order systems sits in the guide to linking Shopify with an ERP system. An ERP, short for enterprise resource planning, is the back-office software that tracks orders, stock and accounts.

What breaks, and who owns it

The objection we hear is that this is theory, and the store needs the feature this month. Fair. The failures below are what that urgency costs six months later.

The last row is the one that ends companies’ quarters. A tool one person understands is not owned by the business. It is on loan from that person.

Decide with three questions, then write the answer down

First, would a competitor gain anything by copying it? If yes, it is probably core, and you build it. If no, rent it.

Second, what happens if the vendor leaves? Write the recovery path in two sentences. If you cannot, the dependency is larger than you thought.

Third, who maintains this in eighteen months? Name a person, not a team. If the honest answer is nobody, buy the version with a support contract, even if building looks cheaper today.

Your next step is a one-page list of every app and every piece of custom code in the store, with an owner’s name beside each line. Most stores cannot complete that page, and the gaps are the answer.

Sources, all checked 21 September 2026. Shopify: the Shopify Scripts deprecation changelog, the Shopify Functions API, Shopify Flow, the checkout upgrade guide and customer events.