Insights

Notes from
inside the code.

Things we have had to explain more than once. Written for the person who will maintain the store after we leave.

Latest · Architecture

9 October 2026 · 8 min read

Large catalogue migrations break on options, not files

Migrating 28,000 products fails when supplier attributes hit Shopify's 3-option ceiling or productSet deletes unmentioned variants. How to map large catalogues.

Archive

Engineering
Custom checkout calculations are lines, not arithmetic
Custom checkout fees and surcharges cannot modify totals directly. How to synchronize line item mutations without orphan items or re-render loops.
9 October 2026 · 7 min read
Integration
Pre-orders need ERP allocation, not manual caps
Selling incoming stock without overselling requires ERP allocation, warehouse filtering, and pagination safety. How to automate Shopify pre-orders from Exact.
7 October 2026 · 8 min read
Engineering
Completeness is calculated, not inspected
A form filled with zeros passes visual inspection and breaks production. How to calculate supplier product readiness across sampling and QC before Shopify sync.
7 October 2026 · 8 min read
Architecture
Shopify hosts the store. Somebody has to host the app
Shopify retries a failed webhook eight times in four hours, then drops the subscription. What self-hosting a custom app commits you to, and how to recover.
6 October 2026 · 7 min read
Engineering
Twenty-three and three-eighths is one size, not five
23 3/8, 23-3/8 and 23.375 are one shelf. To a cart they are three strings, three lines and maybe three prices. Parse once, store one spelling, round up.
6 October 2026 · 7 min read
Architecture
A sample is a product nobody should find
A sample needs a price, stock and an order line, and must never appear in a collection. Shopify’s unlisted status does this, and where it still leaks.
5 October 2026 · 7 min read
Engineering
Plus doesn’t move a big catalogue faster. It fixes it faster
Plus raises the GraphQL limit tenfold, but bulk imports have no rate limit on any plan. What Plus changes for a large catalogue, and what it doesn’t.
5 October 2026 · 7 min read
Architecture
A role belongs to the membership, not the person
Customer tags hold labels, not relationships. When someone leads one team and plays in another, who sees whose sales must be derived. Tags get it wrong.
2 October 2026 · 7 min read
Engineering
A checkout rule that fails open is a suggestion
A validation error always blocks checkout. A validation that crashes does not, unless you said so. Where Shopify checkout rules fail open, and the fix.
2 October 2026 · 7 min read
Architecture
Your source system sent you a string, not an author
Shopify holds a million metaobject entries per definition. The constraint is not capacity — it is knowing how many distinct authors your export contains.
1 October 2026 · 8 min read
Migration
Shopify protects renames, not deletions
Rename a product and Shopify offers a redirect. Delete one and the URL 404s with no prompt. Why consolidation is the operation that loses traffic, and the fix.
1 October 2026 · 8 min read
Migration
The 15 MB limit is not your problem
Splitting the file fixes the 15 MB error and leaves the real problem: CSV import cannot tell you which rows failed. What bulk operations give you instead.
30 September 2026 · 8 min read
Engineering
One product, three barcodes
A case of 24 needs a different GTIN from the can, and Shopify's product record holds one barcode. Where packaging data lives, and what 2026-10 changes.
30 September 2026 · 7 min read
Architecture
You cannot photograph a combinatorial space
Three orientations, five frames and two treatments is thirty images per artwork. Composing the preview instead of storing it, and when a personaliser app is right.
28 September 2026 · 7 min read
Integration
When the stock is wrong, Shopify already knows who wrote it
The usual advice is to audit your apps' write permissions. Shopify already records which app adjusted which item, and the report is filterable by SKU and location.
28 September 2026 · 7 min read
Architecture
Shopify sells the thing; it has no opinion about what the thing is made of
Shopify's digital downloads handle 5 GB per file with no bandwidth limit. What changes when the product is a structured library rather than a file, and where media lives.
23 September 2026 · 7 min read
Engineering
Checkout is a budget, not a canvas
64 KB compiled, no DOM, only Shopify's components, and network access you have to ask for. What the checkout surface actually permits, and how to design inside it.
23 September 2026 · 7 min read
Architecture
The spreadsheet is not the problem: business-managed data as an integration boundary
Shopify has metaobjects for merchant-managed data. When the business reasons in a spreadsheet, the job is to make it a reliable input, not to replace it.
22 September 2026 · 7 min read
Architecture
A balance is a cache: paying money out of a Shopify business
Getting a seller ID onto an order is solved. What has no platform answer is the money you owe outward — the approval workflow, and a balance you can audit.
22 September 2026 · 7 min read
Architecture
Operational email is sent by a person, not fired by an event
Shopify notifications fire on events and render the order. What happens when the operations team needs to tell forty specific customers something the ERP knows.
17 September 2026 · 7 min read
Integration
Analytics on a subset: reporting when the ERP holds the orders
Shopify's analytics are strong, and they only see Shopify's orders. What breaks when the ERP is the system of record, and why a metric definition is an engineering decision.
17 September 2026 · 7 min read
Architecture
Which orders can ship: allocation is a calculation, not a field
Shopify reports inventory per SKU per location. It cannot tell you whether a wholesale order can ship. Why allocation has to be computed, and where the numbers come from.
16 September 2026 · 7 min read
Architecture
Two stores, one product: a sync is a contract, not a mirror
Shopify does not sync products between stores, by design. What a B2B-to-B2C sync has to decide field by field, and the custom ID that stops it creating duplicates.
16 September 2026 · 8 min read
Engineering
Shipping rates that depend on the product, not the product record
Delivery Customization Functions hide, rename and reorder rates. They cannot calculate one. What the Carrier Service API costs, and when a flat rate is the better answer.
11 September 2026 · 8 min read
Architecture
Supplier portals: the operations layer Shopify doesn't have
Shopify models selling to buyers, not buying from suppliers. What a supplier portal has to do, where it should live, and how portal state reaches the storefront.
11 September 2026 · 7 min read
Engineering
Custom price per cart item on Shopify: where price authority actually lives
A Cart Transform function can present a computed price. It cannot compute one and it cannot verify one. Where the authority for a calculated price has to sit.
10 September 2026 · 8 min read
Integration
Exact Online Shopify connector limitations: where standard sync stops
Connectors sync orders, products and stock well. They stop where committed inventory, warehouse filtering and pre-order state begin. What breaks, and how to check.
10 September 2026 · 7 min read
Architecture
Pricing by dimensions: when Shopify variants are the wrong model
Some products have no variant count. How to tell whether you have an enumeration problem Shopify already solved, or a computed-pricing problem that needs a different model.
9 September 2026 · 8 min read
Engineering
Shopify Scripts stopped working: how to reconstruct what they did
Scripts stopped executing on 30 June 2026 and Script Editor is read-only, so the source may be gone. How to audit what your Scripts did from the evidence left in order history.
9 September 2026 · 9 min read

Insights

Want this applied to your store?

The audit is where the writing becomes specific: your theme, your app stack, your numbers.

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Notes frominside the code.

Large catalogue migrations break on options, not files

Custom checkout calculations are lines, not arithmetic

Pre-orders need ERP allocation, not manual caps

Completeness is calculated, not inspected

Shopify hosts the store. Somebody has to host the app

Twenty-three and three-eighths is one size, not five

A sample is a product nobody should find

Plus doesn’t move a big catalogue faster. It fixes it faster

A role belongs to the membership, not the person

A checkout rule that fails open is a suggestion

Your source system sent you a string, not an author

Shopify protects renames, not deletions

The 15 MB limit is not your problem

One product, three barcodes

You cannot photograph a combinatorial space

When the stock is wrong, Shopify already knows who wrote it

Shopify sells the thing; it has no opinion about what the thing is made of

Checkout is a budget, not a canvas

The spreadsheet is not the problem: business-managed data as an integration boundary

A balance is a cache: paying money out of a Shopify business

Operational email is sent by a person, not fired by an event

Analytics on a subset: reporting when the ERP holds the orders

Which orders can ship: allocation is a calculation, not a field

Two stores, one product: a sync is a contract, not a mirror

Shipping rates that depend on the product, not the product record

Supplier portals: the operations layer Shopify doesn't have

Custom price per cart item on Shopify: where price authority actually lives

Exact Online Shopify connector limitations: where standard sync stops

Pricing by dimensions: when Shopify variants are the wrong model

Shopify Scripts stopped working: how to reconstruct what they did

Want this applied to your store?

Notes from
inside the code.