Is mana source instant?

Could you please clarify for me if the Mana source is indeed instantaneous? I'm trying to understand how the mechanism of Mana works in relation to transactions and if there is any delay in accessing the source for these transactions. It would be helpful if you could explain whether the Mana source provides an immediate flow of resources or if there are any factors that might affect its instantaneity. Additionally, I'm also curious about the reliability and stability of the Mana source in terms of its ability to deliver resources instantaneously under various conditions. Thank you for your assistance in clarifying this matter.