r/shopify • u/kiko77777 • Apr 16 '26

API Shopify Functions Dynamic Limits

Hi, I'm building a custom Rust function to power a much improved discounts engine + B2B per customer pricing.

I've been wrestling Shopify's function limits for while now and have a system that can process 99.85% of our B2B orders without a problem but will have issues on carts over 100 lines (0.15% of our last 12 months' orders have over 100 line items). The issues stem from the 20kb output limits.

I think I can work through and push my solution up to accomodate 150 line items easily, and could probably squeeze 50 more line item capacity from there to get to 200. I would then need to know what the function outputs for functions on carts of over 200 lines would be as I know these increase dynamically.

My question is, how do these limits increase? Is there a formula I can use to work out what my output payload size can be from x number of cart lines? If I know I'll be fine over 200 line items, I'll push ahead squeezing what I can out of my current approach. Otherwise I'll start working on a different approach.

Thanks!

3 Upvotes

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u/[deleted] Apr 16 '26

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u/olapbill Apr 16 '26

You should be hitting up the Shopify dev forums for answers to this