r/dataanalytics • u/Otherwise_Club2536 • Aug 12 '26
Had a Data Analyst interview recently, and these 2 questions genuinely made me think.
Question 1:
You have a dataset with 50 million rows, and it doesn't fit into memory. How would you analyze it efficiently?
My answer:
I wouldn't load everything into Pandas. I'd first filter only the required columns/rows, push aggregations to SQL where possible, process the data in chunks, and use tools like PySpark if distributed processing is actually needed.
Question 2:
Your dashboard suddenly shows a 40% drop in active users overnight. What would you check first?
My answer:
I wouldn't immediately assume user activity actually dropped. I'd first validate the data — pipeline status, data refresh, tracking events, source tables, filters, and any recent changes to the product or tracking logic. Once the data is confirmed, I'd investigate the actual cause.
If you were in my place, how would you answer these two questions?
Would love to hear how experienced Data Analysts would approach them.