Instead deploy and configure Azure Cache for Redis. Update the web applications.
Reference:
https://docs.microsoft.com/en-us/azure/architecture/best-practices/caching#managing-concurrency-in-a-cache

Scenario: Users of the ContentUploadService report that they occasionally see HTTP 502 responses on specific pages.
"502 bad gateway" and "503 service unavailable" are common errors in your app hosted in Azure App Service.
Microsoft Azure publicizes each time there is a service interruption or performance degradation.
The az monitor activity-log command manages activity logs.
Note: Troubleshooting can be divided into three distinct tasks, in sequential order:
Observe and monitor application behavior
Collect data
Mitigate the issue
Reference:
https://docs.microsoft.com/en-us/cli/azure/monitor/activity-log

These are valid warm-up behavior options, but are not helpful in fixing swap problems.
Instead update the web.config file to include the applicationInitialization configuration element. Specify custom initialization actions to run the scripts.
Note: Some apps might require custom warm-up actions before the swap. The applicationInitialization configuration element in web.config lets you specify custom initialization actions. The swap operation waits for this custom warm-up to finish before swapping with the target slot. Here's a sample web.config fragment.
<system.webServer>
<applicationInitialization>
<add initializationPage="/" hostName="[app hostname]" />
<add initializationPage="/Home/About" hostName="[app hostname]" />
</applicationInitialization>
</system.webServer>
Reference:
https://docs.microsoft.com/en-us/azure/app-service/deploy-staging-slots#troubleshoot-swaps