---
title: How to Fix Sitecore JSS Middleware Performance
description: Learn how to troubleshoot and resolve Vercel Middleware timeouts and memory errors in your Sitecore JSS application caused by URLs with many query parameters.
url: /kb/guide/how-to-fix-sitecore-jss-middleware-performance
canonical_url: "https://vercel.com/kb/guide/how-to-fix-sitecore-jss-middleware-performance"
last_updated: 2025-11-10
authors: Nick Vigier
related: []
install_vercel_plugin: npx plugins add vercel/vercel-plugin
---

This guide addresses a specific issue where users of Sitecore JSS on Vercel experience `504: MIDDLEWARE_INVOCATION_TIMEOUT` or `500: JavaScript heap out of memory` errors when requests contain a large number of URL query parameters.

Teams deploying Next.js applications with Sitecore JSS on Vercel may observe a pattern of request failures, specifically in the Edge Middleware.

## Symptoms

- **Error Codes:** Function invocations fail with a `504: MIDDLEWARE_INVOCATION_TIMEOUT` status code or a `500` error referencing `JavaScript heap out of memory`.
  
- **Trigger:** The errors are consistently triggered by accessing URLs that contain a large quantity of query string parameters. This is most common with URLs from marketing and ad campaigns, which often include numerous UTM parameters and tracking identifiers (e.g., `utm_source`, `utm_campaign`, `gclid`, `gbraid`).
  

- **Behavior:**
  
  - Requests to the site's root domain or pages without query parameters succeed.
    
  - Requests with a small number of query parameters (e.g., 1-5) may also succeed.
    
  - As the number of parameters increases, the request either slows down dramatically or fails, crossing a threshold that triggers the timeout or memory limit.
    
- **Impact:** This issue can significantly impact the effectiveness of paid marketing campaigns, as users clicking on sponsored links are unable to access the site, leading to a drop in tracked traffic and potential revenue loss.
  

## Root Cause Analysis

Through investigation of multiple occurrences, this issue has been traced back to a specific performance problem within the Sitecore JSS for Next.js library.

- **Affected Version:** The performance degradation is a known issue in **Sitecore JSS version** **`22.2.0`**.
  
- **Technical Explanation:** The logic within the `@sitecore-jss/sitecore-jss-nextjs/middleware` package in version `22.2.0` is inefficient at processing and handling a large volume of `URLSearchParams`. This inefficiency leads to prolonged execution times and/or high memory consumption, eventually exceeding the platform's limits and causing the invocation to terminate. This is a code-level performance issue within the dependency, not a limitation of the Vercel platform.
  

## Troubleshooting and Verification Steps

To confirm if your project is affected by this specific issue, follow these steps:

1. **Check Sitecore JSS Version:** Inspect your project's `package.json` file and look for the version of `@sitecore-jss/sitecore-jss-nextjs`. If the version is `22.2.0` or newer, but less than `22.6.0`, you are likely affected.
   
2. **Reproduce with Test Parameters:** Isolate the issue from specific campaign parameters by testing a URL with an increasing number of generic parameters.
   
   - **Test a working URL (few parameters):** `https://[your-domain]/?p1=1&p2=2&p3=3&p4=4&p5=5`
     
   - **Test a failing URL (many parameters):** `https://[your-domain]/?p1=1&p2=2&p3=3&p4=4&p5=5&p6=6&p7=7&p8=8`
     
     If the first URL loads and the second one times out, it strongly indicates that the quantity of parameters is the trigger.
     
3. **Review Function Logs:** Examine the logs for your Vercel project. Look for function invocations corresponding to the failing requests. You will see error messages confirming the timeout or out-of-memory error originating from your Edge Middleware.
   

## Solution and Workaround

### Permanent Solution

The definitive solution is to upgrade the Sitecore JSS dependency in your project.

- **Action:** Upgrade `@sitecore-jss/sitecore-jss-nextjs` to version **`22.6.0`** **or newer**.
  
- **Reason:** Sitecore has officially addressed and resolved this performance issue in later releases of the library. Upgrading will replace the inefficient middleware logic with a more performant version that can handle a large number of query parameters without timing out.
  

For detailed instructions on upgrading, consult the official Sitecore JSS documentation or contact Sitecore Support to ensure a smooth update process tailored to your specific implementation.

### Temporary Workaround

If an immediate upgrade is not possible, you can mitigate the impact by reducing the number of query parameters used in your marketing campaigns. However, this is not a long-term solution and may limit your tracking capabilities. The recommended path is to upgrade the dependency.