The problem
When a retail sale becomes an unintended wholesale discount.
A trade lighting brand’s Shopify B2B catalog applied its percentage discount to whatever the current price was — so a retail sale quietly cut wholesale prices too. A $100 product at 20% off should stay $80; a 30% retail sale dragged it to $56. The fix had to preserve the agreed discount off original retail, whatever changed the price.
Retail promotion
$70
$100 − 30%. Retail gets the sale, as intended.
Wholesale without Trade Lock
$56
$70 − 20%. Both discounts stacked.
Wholesale with Trade Lock
$80
$100 − 20%. Agreed wholesale discount off original retail.
Illustrative pricing math, not measured merchant savings.
What was built
Metra Price Automation, built by Eryn Tech.
We built Metra as a Shopify app whose Trade Lock keeps B2B catalog prices at the configured discount off original retail during sales, alongside scheduled price changes with automatic reverts. This page covers why it was built and how it’s engineered — features, pricing, and merchant setup live on the product page.
Engineering approach
Pricing automation needs to account for changes outside the app
Metra’s engineering includes monitoring product pricing and using price and compare-at-price signals to identify relevant changes. Its background processing uses Sidekiq and Shopify’s GraphQL API to perform pricing operations.
The implementation is intended to support pricing workflows where changes may originate from multiple sources, including scheduled jobs, manual edits, and external systems.
The results
From a merchant pricing problem to a live Shopify product.
- Metra has been on the Shopify App Store since May 2026. Source: App Store listing
- A trade lighting merchant runs Trade Lock in its live store. Source: Merchant account
No revenue, conversion, or savings claims.
What this demonstrates
Business rules are often more complicated than the interface suggests.
The underlying problem wasn’t simply how to schedule a sale. It was how to preserve an established pricing rule when multiple systems and workflows could change the product price.
Metra demonstrates Eryn Tech’s experience building Shopify applications around specific operational requirements, including pricing logic, background processing, and integrations with Shopify’s APIs.
Stack
- Shopify
- Shopify GraphQL API
- Ruby on Rails
- Sidekiq
- Background Jobs
- Pricing Automation