Issue with Mongoose 6+ Database Switching Middleware in Express.js

I’m implementing an Express.js middleware to switch between different MongoDB databases using Mongoose based on the request API URL. The middleware is supposed to disconnect from the current database and connect to a new one depending on the API URL path. However, I’m facing some issues with the implementation, and I would appreciate some guidance.

Here’s the middleware code:

const switcher = async (req, res, next) => {
try {
const [, second] = req.url.split("/");
const connection = second === "auth" ? process.env.AUTH_DB_URL : process.env.STORAGE_DB_URL;

if (mongoose.connection.readyState !== 0 && mongoose.connection.client.s.url !== connection) {
  await mongoose.disconnect();
  await mongoose.connect(connection, { keepAliveInitialDelay: true });
  console.log("Connected to", connection);
}

next();
 } catch (err) {
console.error(err);
return res.status(500).send({ status: 500, message: "Internal Server Error" });
}
};

Steps Taken:
The API URL path is split to determine which database to connect to.
The middleware checks if the current connection is different from the desired one.
If different, it disconnects from the current database and connects to the new one.

Problems Encountered:
The middleware may not properly switch databases under certain conditions.
Potential issues with mongoose.disconnect() and mongoose.connect() not being called correctly.
Concerns about handling concurrent requests and ensuring connections are properly managed.

Seamless Switching: I expected the middleware to seamlessly disconnect from the current database and connect to the new one based on the request URL.

Correct Database Operations: After switching, subsequent database operations should be performed on the newly connected database.

No Interruption: The middleware should handle concurrent requests efficiently without causing interruptions or errors.