Write multitenant app in only one Atlas cluster

Hello, im developing a sale manager application for multitenant
I will start about 800 client and it can be up to 3000 around 1 year
My app have one db for manage user account
Each user have one separate db where store product, order, inventory…
I store all db in one Atlas cluster for easy manager
Each request my nodejs app will read the header and switch moongoose to mongodb corresponding
Is there any problem with my design structure?
And what is i must care for this design?(index example…)

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