Shopify Carrier Service Shipping Rates Developer Needed (timeouts, caching, fallback logic)

I'm using Shopify's Carrier Service (dynamic shipping rates) and my shipping provider's API occasionally responds in 12+ seconds. Shopify has strict timeouts, so those slow responses cause rate requests to fail and Shopify falls back to backup rates too often. I can't improve the shipping provider's API speed, so I need a reliable alternative approach that keeps rates accurate without breaking checkout.

I'm looking for a developer who has implemented carrier-calculated rates for Shopify before and has dealt with real-world timeout issues.

Requirements:
- Experience with Shopify Carrier Service API
- Implement caching layer for shipping rates
- Build fallback logic for timeout scenarios
- Ensure accurate rates display at checkout
- Less than 1 month timeline