Function open_with_pool_size 

pub fn open_with_pool_size(
    database_filepath: &Path,
    connection_pool_size: NonZeroUsize,
) -> Result<(DbWriter, DbReader), DatabaseError>

Opens a database over database_filepath with the given reader-pool size. The writer is always a single connection.

Returns the write handle and the reader handle as separate values rather than one shared object, so read-only and write access are distinct, non-interchangeable capabilities: a component handed only a DbReader has no way to write. The DbWriter is not Clone, so there is at most one writer owner (mirroring the max_size(1) writer pool).