@DocBrown is correct, but I'd like to offer a condensed revision with practical focus.

If a database is accessed via connection URI from multiple components, it is a shared mutable state. But the database handle is usually explicitly passed around, making it non-shared.

Shared variables can be easily made non-shared by reducing their visibility and explicitly passing references to them, but this is never done. Instead, they are sometimes wrapped in a Singleton, which is also a shared (and often mutable) state and achieves nothing.

@DocBrown is correct, but I'd like to offer a condensed revision with practical focus.

If a database is accessed via connection URI from multiple components, it is a shared mutable state. But the database handle is usually explicitly passed around, making it less shared.

Shared variables can be easily made non-shared by reducing their visibility and explicitly passing references to them, but this is never done. Instead, they are sometimes wrapped in a Singleton, which is also a shared (and often mutable) state and achieves nothing.

@DocBrown is correct, but I'd like to offer a condensed revision with practical focus.

If a database is accessed via connection URI from multiple components, it is a global mutable state. But the database handle is usually explicitly passed around, making it non-global.

Shared variables can be easily made non-global by reducing their visibility and explicitly passing references to them, but this is never done. Instead, they are sometimes wrapped in a Singleton, which is also a shared (and often mutable) state and achieves nothing.

@DocBrown is correct, but I'd like to offer a condensed revision with practical focus.

If a database is accessed via connection URI from multiple components, it is a shared mutable state. But the database handle is usually explicitly passed around, making it non-shared.

Shared variables can be easily made non-shared by reducing their visibility and explicitly passing references to them, but this is never done. Instead, they are sometimes wrapped in a Singleton, which is also a shared (and often mutable) state and achieves nothing.