Shopify Functions and checkout extensions, where the platform runs your logic.
Since checkout became extension-only, the rules that used to live in scripts and theme edits belong in Shopify’s own extensibility surfaces: Functions for discount, delivery and payment logic, checkout UI extensions for what the buyer sees, theme app extensions for the storefront. Code in those surfaces runs on Shopify’s infrastructure, at Shopify’s speed, and survives theme upgrades.
We have shipped discount, upsell and bundle logic into production this way, and the failure modes are specific: a Function has a strict execution budget, a checkout extension cannot reach your backend on the critical path, and a theme app extension has to degrade when a merchant moves the block. Those constraints shape the design from the first sketch.
What the engagement actually contains.
Native Shopify extensibility where the platform actually runs your logic — discounts, delivery, payments and checkout UI.
- 01
Shopify Functions
Discount, delivery customisation, payment customisation, cart transform and validation logic written to run inside the platform’s execution budget, with the input query kept small on purpose.
- 02
Checkout UI extensions
Banners, fields, upsells and post-purchase surfaces that behave under Shopify’s rules — including what happens when the buyer changes their mind halfway.
- 03
Customer account extensions
Order status, reorder and self-service flows in the new customer accounts, so support stops answering the same three questions.
- 04
Theme app extensions
App blocks a merchant can place and configure in the theme editor — no Liquid surgery, and nothing that breaks the next time the theme updates.
- 05
POS UI extensions
The same product logic on the retail floor, for merchants whose in-store staff need it too.
Where we have already done this.
Our own catalogue, not a case study written for this page. Every name below is public software you can open right now.
Easy Discounts by DevCloud
Quantity breaks and bulk discounts, created in a couple of clicks — discount logic in the merchant’s hands rather than in a developer’s backlog.
Smart Upsells and Bundles
AI-powered upsell, cross-sell and bundle widgets running on live product and cart surfaces.
Feedfy: Shoppable Instagram
4.8 rating — storefront surfaces that have to add to cart in one tap without wrecking the page.
What people ask before starting one of these.
We still have Shopify Scripts. What now?
Scripts belong to the old checkout and do not come with you. The equivalent logic goes into Functions, which is usually a rewrite rather than a port — the model is different enough that translating line by line produces something slower and harder to reason about than starting from the rule you actually want.
Can a Function call our API?
No, and that is the constraint worth designing around: Functions run inside Shopify with no network access. Anything they need has to be in the input query — usually metafields you keep in sync ahead of time. We size that sync as part of the build.
Do we need Shopify Plus for this?
Not for most of it. Functions, theme app extensions and customer account extensions work outside Plus; some checkout UI placements and the deepest checkout customisation still require it. We will tell you which side of that line your requirement falls on in the first answer.
More general questions — cost, ownership, what happens after launch — are answered on the home page FAQ.
Have a functions & checkout extensions project?
Send the spec and an engineer answers within 48 hours — how we would build it, the rules that apply, and a price. The first working build follows days later, not quarters.
- A costed answer within 48 hours
- A working build you can click in days, not quarters
- Fixed price or T&M, quoted before we start
- Server, domain, SSL and monitoring handled — or shipped into your cloud
- You own the repo, the Partner account and the infrastructure
Prefer the company site? devcloudsoftware.com