Back In Stock vs Buy with Prime: Shopify Performance Comparison
Back In Stock wins with Grade B vs Grade C — a one-grade performance difference that compounds on mobile devices.
Both apps provide general Shopify store enhancement functionality for Shopify stores. This page presents StackConflict’s independent lab results for both — measured in a clean-room environment with no other apps installed.
Head-to-Head Metrics
| Metric | Back In Stock | Buy with Prime | Faster |
|---|---|---|---|
| Overall Grade | B | C | Back In Stock |
| JS Payload | 132.07 KB | 184.43 KB | Back In Stock |
| CPU Desktop | 36 ms | 19 ms | Buy with Prime |
| CPU Mobile | 60 ms | 121 ms | Back In Stock |
| Layout Shift | 0.0 | 0.0006 | Back In Stock |
Mobile CPU measured with 4× CDP throttle (mid-range Android). Tested 2026-05-30.
Back In Stock — The Faster Option (Grade B)
Back In Stock scores Grade B with a JS payload of 132.07 KB and 36 ms desktop CPU execution. Mobile CPU: 60 ms. It passes every StackConflict threshold for payload, CPU, and layout stability — making it safe to install on any storefront including mobile-first stores where Time-to-Interactive directly impacts conversion.
View full Back In Stock speed report →
Buy with Prime — The Heavier Option (Grade C)
Buy with Prime scores Grade C with a JS payload of 184.43 KB and 19 ms desktop CPU execution. Mobile CPU: 121 ms. This places it in the heavier half of StackConflict’s benchmark dataset — merchants running mobile-first stores should evaluate whether the feature value justifies the performance tradeoff.
View full Buy with Prime speed report →
When to Choose Back In Stock
- You need its specific features and can monitor its mobile impact
- Your other apps are lightweight (Grade A) so there is headroom
- You are on desktop-skewed traffic where CPU cost matters less
When to Choose Buy with Prime
- Its unique feature set has no lighter equivalent in StackConflict’s database
- Your store traffic is predominantly desktop
- You have already removed or lightened other heavy scripts to compensate
Performance Verdict
Winner: Back In Stock — Back In Stock wins with Grade B vs Grade C — a one-grade performance difference that compounds on mobile devices.
About This Test
StackConflict measures each Shopify app in an isolated clean-room environment — a single development store, no other scripts, Playwright-controlled browser. V8 CPU cost is the ScriptDuration delta before and after injection. CLS is captured from the same browser session. Results represent the median of three independent runs with outliers removed.
Data from the StackConflict Lab. Last updated 2026-05-30.