Dynamic Range Sizes in Formulas

I had a question on variable length arrays within complicated array formulas, because the data size would change daily, but I couldn't use whole column references because it slowed everything down. While building my sample sheet for upload here, I had an idea and solved my own question. Thought I would share my solution here;

Scenario: I have values in Column K, starting at K2. I need to SUM them. The number of values is variable.

Example formula (correct output, slow calculation speed)
=SUM(K:K)


Solution:
=SUM(OFFSET(K2,,,COUNTA(K:K)))



Note: SUM formula is a placeholder. I know it is not a complicated array function, and I know that this specific example wouldn't be slow enough to need a solution like this. It is just to show how the range is replaced.

Note 2: This solution assumes no blank rows in Column K.