[inglor]

In a gist: MobX just keeps the whole dependency graph of what data needs to update when what computed runs. Excel can't do that because it has to be able to work on large files with impartial data.

[aatd86]

Aren't excel formulas the expression of data dependency graphs?

In which case it is kept in the document?

[coldtea]

Isn't the Excel document still in memory?