Multiple databases for one project

We are creating a multi vendor food delivery system and we want to create 3 databases. One database will have vendors profile, category, food and fav user food collections , database 2 will have cart item , discount, order and location collections and database 3: will have chat room, chat message support collections.

Is it efficient to do it this way or it does not matter ?

It really depends on how you can manage the internal logic and understand it.

Different Database is also fine as it gives more understanding and readability. Example -

1. Database - Vendors
   └── Collections - Some logic based different collections or a single one to group vendors.

2. Database - Misc [locations, etc.]
   └── Collections - same as above []

3. Database - Chats
   └── Collections - different chat documents per chat room.

Another Database Logic -
Database - Delivery App
└── Collections -
└── Vendors -> List all vendors
└── Misc -> Add Coupons, Menus, etc

Database - Chats
└── Collections -
└── Chat-[VENDOR_ID-USER_ID]
└── Chat Documents.

So it does not change the speed of the system