dynamically switching db (when dbs are created dynamically, so cannot use aliases)

i will try to describe my usecase here:
i am using a multi tenant db model in which each client has their own database( due to very specific business use case). suppose i have to get the users details for a client x that has its own db named x,
these are the steps i need to execute to get the data:

• connect to admin db & get admin details
• connect to x db & get list of users
• connect to cc db & insert some data

all of the above operations are to be executed in a single request to get the required results.

basically i need to map a Document class to multiple dbs which are created dynamically(as clients register) so i cannot hard code this in the document definition.

i guess the default behavior of mongoengine is to bind each Document to a specific database as soon as the code defining the document is executed, but we somehow need to bind documents to a db's dynamically.

other issues that are almost related:
#1610
any specific architectural reason to bind a document to a database at the first execution of document?

Start by reading the document-to-database binding behavior described in the issue and comparing the use case with related issue #1610. Trace how a Document is associated with a database during definition, then establish the scope and tests needed for switching among dynamically named databases within one request; no files or existing tests are identified here.