Shopify Developer Needed – Build Custom Carrier Service App for LTL Freight

I operate a Canadian Shopify store that ships pallet-sized LTL freight only (no parcel shipping).
I need an experienced Shopify developer to build a custom Carrier Service app that:
Connects to Freightcom's API
Retrieves real-time LTL shipping rates
Returns those rates to Shopify checkout using Carrier Calculated Shipping
Optionally adds a configurable markup percentage or flat handling fee
Allows returning either:
Cheapest rate only, OR
Top 2–3 rate options
Project Scope:
Create private Shopify app
Host middleware (Heroku, Render, or similar)
Connect to Freightcom API
Handle residential vs commercial logic
Handle liftgate option logic
Return rates in Shopify-required JSON format
Basic admin configuration (markup % field preferred)
Store Details:
Canada-based
Ships Canada only
All products are pallet-sized freight
No parcel logic needed
No international shipping
Requirements:
Proven experience building Shopify Carr...