🎯 Interview & Career · Chapter 6

Explaining your projects in 90 seconds

“Walk me through your current project” is the question you'll be asked in almost every round — and the one candidates prepare least. Your 90-second answer decides what the next 30 minutes are about.

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The basics

The project pitch is a 60–90 second spoken summary of a project you worked on: what problem it solved, what you built, one hard decision, and the result. It's the answer to “tell me about your project” — asked in technical, manager and HR rounds alike.

Why it matters: the interviewer uses your pitch to choose what to dig into. A tool list (“Kafka, Spark, Airflow, Snowflake”) invites random questions about any of them. A pitch built around a problem, a number and a decision invites questions you prepared for.

The mental model — six beats:

1. Problem — who needed what, and why it mattered (with a number)
2. My role — what you owned
3. Shape — the architecture in one sentence: source → processing → storage → consumer
4. Hard part — one decision or trade-off, and why you chose it
5. Result — what changed, measured
6. Hook — an open door for the follow-up you want

The pitch is an index, not the book. Detail comes when they ask.

Words to know: pitch, hook, drill-down, numbers you must know.

Explained

Pitch A: “I worked on a data platform using Kafka, Spark, Airflow, Snowflake, dbt and Tableau. We ingested data from multiple sources, transformed it and built dashboards.”

Pitch B: “Meghalaya Cabs' finance team was reconciling driver payouts by hand — two people, three days every week, and still about ₹2 lakh of errors a month. I built the pipeline that replaced it…”

A tells them nothing and invites a random quiz on six tools. B tells them why it mattered and makes them want the next sentence.

The film trailer

A film trailer is two minutes long and doesn't show the whole film.

It shows the world in one shot, the hero and what they want, one moment of real conflict, and a hint of how it turns out — then stops, so you want to see the rest.

A trailer that lists the cast, the cameras and the shooting locations would be useless, however impressive the equipment.

Your pitch is the trailer. The deep-dive is the film. Show the problem, your role, the conflict (the hard decision) and the outcome — and leave them wanting to ask.

The six beats

Roughly 15 s / 10 s / 15 s / 25 s / 15 s / 5 s. The hard part gets the most time because it's the only beat that proves judgement.

A 90-second pitch, spoken

“At Meghalaya Cabs, finance was reconciling weekly driver payouts by hand — two analysts, three days a week, and still around ₹2 lakh a month in errors. [problem]

I owned the new payouts pipeline end to end, in a team of three. [role]

Ride and payment events land in S3, a daily dbt job builds an append-only earnings ledger in Snowflake, a weekly job computes payouts, and a reconciliation job matches them against the bank's settlement file. [shape]

The hardest call was handling late refunds. Updating last week's rows would be simpler, but finance needs to see exactly what was paid. So I made the ledger append-only and booked late changes as adjustments in the current week. [hard part]

Manual reconciliation went from three days to about an hour of review, and payout errors dropped to under ₹10,000 a month. [result]

I'm happy to go deeper on the ledger design or how we made payouts idempotent.” [hook]

Numbers you must know about your own project

VOLUME      rows/day ......... ~1M rides, ~8M events
            data/day ......... ~16 GB raw, ~3 GB Parquet
            history .......... 2 years, ~6 TB
SPEED       freshness SLA .... daily by 06:00 / 15 min for ops
            job run time ..... 22 min (was 3 h)
RELIABILITY incidents/month .. 4 → 1
            tests ............ ~200 dbt tests, 12 blocking on money
COST        warehouse ........ ~₹X lakh/month (or ‘we cut it ~30%’)
PEOPLE      team size ........ 3; I owned ledger + recon

The first drill-down is almost always “how much data?” Hesitating on your own project's volume makes the whole story sound second-hand. Round numbers are fine; not knowing is not.

How pitches go wrong

• The tool list. Six technologies, no problem. Invites a quiz on all six.
• The chronology. ‘First we did X, then in Q2…’ — five minutes before anything interesting.
• ‘We’ all the way. They can't tell what you did. Say your part plainly.
• No numbers. ‘Large data’, ‘much faster’. Use magnitudes.
• Claiming everything. Owning the whole platform as a junior invites probes you can't survive. Claim what's yours.
• A hook you can't defend. Never mention a topic you can't go ten minutes deep on.
• NDA panic. You can anonymise: ‘a large fintech’, ‘tens of millions of transactions a day’. Shapes and magnitudes are fine; client names and secrets aren't.

Problem, role, shape, hard part, result, hook — in 90 seconds.

The pitch is an index, not the book. Know your numbers, and only hook what you can defend.

The drill-downs to prepare

After the pitch, expect some of these — prepare a 1-minute answer for each:

• “Draw the architecture.” → boxes and arrows, data volumes on the arrows.
• “Why Snowflake / dbt / Airflow and not X?” → the requirement that decided it, honestly including ‘it was already there’.
• “What happens when it fails?” → retries, idempotency, alerts, a real incident.
• “What would you change if you started again?” → one real regret, specific.
• “What was your exact contribution?” → the parts you designed, wrote, or decided.
• “How did you test it?” → the layers, one test that caught a real bug.

‘It was already there’ is a perfectly good answer for a tool choice, followed by “but I'd keep it because…” or “I'd reconsider it because…”.

Words to know

In two minutes

• Your project pitch is asked in almost every round, and it steers the rest of the conversation.
• Six beats: problem, your role, architecture in one sentence, one hard decision, measured result, a hook.
• Lead with the business problem and a number, not the tool list.
• Say the architecture as one flow sentence; save the diagram for when they ask.
• Pick one hard decision with a trade-off — that's where interviewers dig and where you shine.
• Know your project's numbers cold: volume, latency, run time, cost, team size, your share.
• Prepare three depths: a 30-second version, the 90-second pitch, and a 10-minute whiteboard walk-through.

Test yourself

There are 8 questions, 3 puzzles and 5 recall cards for this lesson in the app — the recall cards come back on later days, just before you would forget.