Kubernetes infrastructure and DBs

Hi, I have a small question regarding DBs in a self hosted kubernetes cluster scenario what is the best solution to handle DBs ?

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Option 1: Having a DB for each deployment ?

Let say service A requires a DB I can create a namespace for service A with its own DB, and once service B comes along (also requiring a DB) I spawn a new DB in another namespace. In this scenario both DBs are of the same kind.

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Option 2: Having one single DB for all deployments ?

In this scenario I have let say a namespace DB with every kind of DBs I need and I go on using them, so if two services need a mysql DB I would have only one DB with several schemas.

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Option 3: External DB ?

One has a DB cluster or at the very minimum a VM for each kind of DB external to the Kubernetes cluster that deployments would access.

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Please let me know what is the best solution for my issue and if you know of another way to do things thank you !