IIS Application Pool issue when hosting multiple React applications , backend communication breaks after adding third app

[Samanthapudi-Shakeer]

I am hosting multiple React frontend applications under the same IIS Application Pool sites.

Current setup:

All React apps are deployed as separate IIS applications/sites

All of them are mapped to the same Application Pool

Each React app communicates with its respective backend (API) / NodeJS

The backend services themselves are running correctly and are reachable

Observed behavior:

When 2 React applications are hosted in the same application pool, everything works correctly

Frontend loads

API calls succeed

Frontend–backend communication works consistently

When I deploy a 3rd React application into the same application pool:

All 3 React frontends render properly in the browser

However, the first two applications completely stops working or intermittently fail to communicate with their backends.

When making requests from the React frontend, the request neither gets redirected nor returns any response. The frontend remains loaded, but the API call appears to hang or fail silently.

Sometimes API calls work, sometimes they fail (no consistent pattern) like 400, 500 while we are chasing 200.

There is no issue with rendering only the frontend–backend “handshake” breaks

If I remove the 3rd React application, the first two immediately start working normally again

Important comparison:

When I host multiple Django applications (4–5 apps) under IIS (using the appropriate setup), I do not face this issue

The problem seems to occur only with React applications, not with Django apps or others probably.

Additional notes:

No major configuration changes are made between hosting the 2nd and 3rd app, except adding another React app to the same pool

We have taken care of redirection / URL rewrites in IIS also.

My questions:

Why does hosting a third React application in the same IIS application pool cause backend communication issues for the existing apps?

Is this related to:

IIS application pool limits?

Node/React build configuration?

Static file hosting under IIS?

Port, proxy, or environment variable conflicts, web config rewrite issue ?

Is it recommended to host each React app in a separate application pool, and if so, why?

Why does this issue not occur with Django applications under similar conditions?

How many React applications can be hosted on a single IIS application pool ?

Are we having issue with IIS or React Framework.

Looking forward for answer...

Any insights regarding this would be appreciated.