40 real data interview questions + the habit system to actually retain them

(FREE Guide)

5 years ago, I was studying for data science interviews.

• Watching tutorials,

• taking notes,

• building a Notion doc full of SQL concepts.

I was ready, or so I thought.

I blanked during a SQL screen (after studying 5+ years of hardcore applied maths…)

It was not even something new. On a GROUP BY with HAVING. A concept I had literally watched a tutorial about the week before.

That failure broke something open for me because I knew the concept on paper.

I’d just never practiced it under any pressure. That’s a different problem. And no amount of rewatching would fix it. I needed a system.

So I went back to something I’d read in James Clear’s Atomic Habits: habits stick when they’re small enough to start, consistent enough to stack, and tied to an identity you’re trying to build.

And I wondered: what if I rebuilt my interview prep around those four laws instead of around a curriculum?

That’s what Atomic Data Interview is.

It’s a free 11,000-word guide built on James Clear’s four laws of habit formation, with 40 real interview questions across the four domains that show up in every data science screen:

• SQL,

• Statistics,

• Machine Learning, and

• Python.

It’s the system I wish I had when I was preparing my data interviews, and the one I’ve since used with the people I mentor.

Here’s what’s inside:

• 40 real interview questions across SQL, Stats, ML, and Python — the ones that actually come up (window functions, A/B test design, bias-variance tradeoff, pandas transformations)

• A habit protocol for each domain — how daily reps build fluency you can actually recall under pressure

• The Interview Simulation System — a 3-step loop using the Feynman Technique to practice like it’s real

• A 90-day Atomic Habit Plan — daily minimums, domain rotation, and weekly review templates

• A “where to start” answer — because most people drown in resource selection long before they get to the SQL

Get it here:

And the best part is that it’s completely free.

If you’ve been watching, re-watching, taking notes, and still freezing in interviews — this is for you.

Keep building,

Penelope

PS: This started as a personal doc and turned into 11,000 words with templates, habit trackers, and a full 90-day plan. I hope it saves you the SQL screen failure I had to go through first.