NopCommerce 4.30 slow at ViewResultExecutorand action Nop.Web.Controllers.HomeController.Index

I have upgraded to nopCommerce 4.30 from 4.20 for faster speed. But it is actually much slower. For example, the start up is very slow. It can take more than 12 s to get a response for initial post. It just does nothing during the period. Here is the debug log:

Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor: Information: Executed ViewResult - view Index executed in 60535.5554ms.
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker: Information: Executed action Nop.Web.Controllers.HomeController.Index (Nop.Web) in 60676.2995ms
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executed endpoint 'Nop.Web.Controllers.HomeController.Index (Nop.Web)'

There are no SQL queries in the debug log. So it may not be caused by slow database queries. What's the real issue? How do I debug this?

The debug log since refreshing page:
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/1.1 GET http://localhost:15536/  
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executing endpoint 'Nop.Web.Controllers.HomeController.Index (Nop.Web)'
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker: Information: Route matched with {action = "Index", controller = "Home", area = ""}. Executing controller action with signature Microsoft.AspNetCore.Mvc.IActionResult Index() on controller Nop.Web.Controllers.HomeController (Nop.Web).
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor: Information: Executing ViewResult, running view Index.
System.Net.Http.HttpClient.default.LogicalHandler: Information: Start processing HTTP request POST https://bebooks.com.au/scheduletask/runtask
System.Net.Http.HttpClient.default.ClientHandler: Information: Sending HTTP request POST https://bebooks.com.au/scheduletask/runtask
System.Net.Http.HttpClient.default.ClientHandler: Information: Received HTTP response after 45.0842ms - NoContent
System.Net.Http.HttpClient.default.LogicalHandler: Information: End processing HTTP request after 49.5168ms - NoContent
Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor: Information: Executed ViewResult - view Index executed in 26914.1323ms.
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker: Information: Executed action Nop.Web.Controllers.HomeController.Index (Nop.Web) in 26919.4484ms
Microsoft.AspNetCore.Routing.EndpointMiddleware: Information: Executed endpoint 'Nop.Web.Controllers.HomeController.Index (Nop.Web)'
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request finished in 27101.8871ms 200 text/html; charset=utf-8
Microsoft.AspNetCore.Hosting.Diagnostics: Information: Request starting HTTP/1.1 GET http://localhost:15536/Themes/NobleTheme/Content/css/jquery-ui-1.10.3.custom.min.css  
Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware: Information: Sending file. Request path: '/NobleTheme/Content/css/jquery-ui-1.10.3.custom.min.css'. Physical path: 'D:\Users\brw\Documents\My Web Sites\nopCommerce_4.30_Source\src\Presentation\Nop.Web\Themes\NobleTheme\Content\css\jquery-ui-1.10.3.custom.min.css'

The site URL is https://bebooks.com.au

Anyone can point out what could be cause of the 17 s request?

Slow Requests Detected on Azure. It didn't have the issue with nopCommerce 4.20.

Steps to reproduce the problem:
1. Run nopCommerce 4.30 and 4.20 websites with two identical databases (copy) side by side on local server through Visual Studio debugger.
2. Turn on mini profilers on each.
3. The result for reloading home page: 4.30 spends 56s in request while 4.20 1.5s. 4.30 is 40 times slower in reloading the home page than 4.20. Please the mini profiler screenshots below.

The same issue occurs on production server https://bebooks.com.au. The slow request seems across many pages. The whole site becomes slow and unusable.

We believe 4.30 should be faster. But why there is such an unreasonable long request in 4.30? Did I miss something? How to investigate it further?

Mini profiler results of 4.20


Mini profiler results of 4.30

The above tests were conducted in Visual Studio debugger and an admin user is logged in.
If the user logs out, it's faster.

The home page's reloading time is about 10 times longer when a user is logged in. Why there is such a big difference in reloading time? Please point  out the possible causes.

These tests were conducted on a production server.

User logged out:



Admin user logged in: