SplitFlow:
idea to production
SplitFlow is our Shopify app that splits orders into separate shipments, using rules the merchant sets. Here's how it was built, got through App Store review and found its first paying merchant — and how we tracked down an undocumented webhook gap along the way.
Rules in, separate shipments out
Some items in an order need to ship on their own — they come from a different vendor, carry a particular tag, or would push a parcel past a carrier's weight cap. In SplitFlow the merchant describes that once, as rules. From then on, matching orders are split into separate shipments — Shopify fulfillment orders — automatically.
Match items by
Or cap every shipment
For example, a carrier's 20 kg cap per parcel.
Only fulfillment changes. Order totals, payment, inventory and reporting stay untouched.
When the vendor is “Acme Dropship”, move those items into their own shipment.
When a product tag is “pre-order”, move those items into their own shipment.
When a shipment weighs more than 20 kg, split it into shipments of up to 20 kg each.
From first build to first paying merchant
A short build, a single review round-trip, and a first paying merchant about ten weeks after launch.
First version
The first working version was built in about 3 days, by one engineer working with AI-assisted tooling.
About 3 daysSubmitted for review
Submitted to the Shopify App Store for review.
11 July 2026One review round-trip
Shopify's reviewer asked for a real screencast of the working app, not marketing slides. We recorded one — that was the single round-trip.
July 2026Approved & published
Approved and published on the Shopify App Store, where any merchant can install it.
15 July 2026First paying merchant
About ten weeks after launch, the first merchant subscribed to the $49/month plan.
Late September 2026Their first week
SplitFlow evaluated 400+ of their real orders and split 90+ of them automatically — with zero errors.
Week oneThe webhook that never came
Some orders were only being picked up by the 15-minute safety net. The cause was on Shopify's side — and it isn't documented.
The symptom
SplitFlow normally starts work when Shopify sends the fulfillment_orders/order_routing_complete webhook. For orders paid through certain offsite payment gateways, it never arrived — so those orders waited for the safety-net job that rechecks orders every 15 minutes.
The investigation
Shopify's own webhook delivery logs gave the answer. These weren't failed deliveries: for those orders, the event was never generated at all. The behaviour isn't documented.
The fix
We added orders/create as a second trigger. Both triggers go through one shared atomic claim, so whichever arrives first splits the order — exactly once.
The result
For those orders, time-to-split dropped from up to 15 minutes to about 40 seconds. The 15-minute safety net stays in place as a backstop.
How it's kept reliable
SplitFlow works on real stores' live orders, so the safety nets are part of the build — not an afterthought.
The stack
Shopify's app template and APIs, Prisma with SQLite, and Docker on a single VPS.
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