Dave · Data Scientist
Updated · 2026-09-22

Dave Data Scientist
Interview Questions & Guide 2026

THE 60-SECOND BRIEF

As a Data Scientist at Dave, you are at the intersection of financial technology and user-centric data analysis. Your work directly impacts how Dave delivers accessible financial products, helping to optimize decision-making models that support the financial health of millions of users. You are not just building models in isolation; you are solving real-world problems related to financial inclusion, risk assessment, and personalized product experiences.

If the team owns experimentation, expect depth past a two-sample test: minimum detectable effect and its roughly inverse-square-root dependence on sample size (holding power, significance level and variance fixed), variance reduction from pre-period covariates, interference between units, and when a sequential design is the right call.

PracHub has no confirmed round sequence for Dave. Treat the sections below as preparation areas and confirm the format with your recruiter.

Separate authorization, settlement and dispute outcomes cleanlyDecompose expected loss into PD, LGD, EADReconcile amounts in minor units and currency

26 min read

Practice 12 Data Scientist prompts
1Candidate experiences ↗Read their reports
12Practice promptsAcross five skill areas
3With worked solutionsIncluded in the practice prompts

As a Data Scientist at Dave, you are at the intersection of financial technology and user-centric data analysis. Your work directly impacts how Dave delivers accessible financial products, helping to optimize decision-making models that support the financial health of millions of users. You are not just building models in isolation; you are solving real-world problems related to financial inclusion, risk assessment, and personalized product experiences.

The role requires a blend of technical rigor and business intuition. You will be expected to translate complex data signals into actionable strategies that move the needle for the business. Because Dave operates in a fast-paced environment, you will need to be comfortable navigating ambiguity, collaborating across cross-functional teams, and delivering insights that balance innovation with operational stability.

The most successful candidates at Dave demonstrate a strong ability to connect technical output to business outcomes. Focus your preparation on explaining the 'why' behind your models, not just the 'how.'

01

Preparation focus

editorial

No round sequence has been reported for this company, so work the categories below and confirm the format with your recruiter.

What to demonstrate

  • Breadth across SQL, experimentation and product reasoning
  • Ability to state assumptions before choosing a method

How to prepare

  • Drill the practice exercises below and time yourself
  • Prepare three quantified stories about decisions you drove
PracHub interview preparation framework

1 candidate reports. Individual accounts describe a particular role and hiring cycle.

Machine Learning Engineer

Dave Machine Learning Engineer Interview Experience — A Long Python OA and Live Data Exercise

Online Assessment → Technical Screen

After I spoke with the recruiter, I received a fairly long online assessment. It had multiple-choice questions about the language used for the role, which in this case was Python, along with syntax questions. It also had two longer CoderPad questions. The first involved data manipulation. The second was a very long debugging problem with multiple steps. Retakes were allowed, so I could contact th…

Read full experience

PracHub editorial advice for the preparation topics above.

01

Recalibrating an underwriting cutoff on approved and funded applicants only

Rejected applicants have no repayment outcome, and they were rejected because the incumbent model scored them badly, so the missingness depends directly on the outcome being modelled. Reject inference by augmentation or parcelling fills the gap using the incumbent model's own assumptions, which means it can confirm those assumptions but cannot test them. The only genuinely new information about the reject region comes from bureau performance on rejects who borrowed elsewhere, or from a deliberately randomised approval band around the cutoff.

02

Reading the most recent months of fraud and dispute rates as final

Consumer dispute rights commonly run around 120 days from the transaction or expected delivery date, and several reason codes run considerably longer, so the disputes belonging to a recent transaction month have simply not been filed yet. Any chart attributed by transaction date therefore slopes down at the right edge regardless of what is happening. The fix is to report only matured cohorts, or to apply development factors estimated from completed months and to show the estimate as an estimate.

03

Reporting a p-value with no effect size or interval

Give the estimated difference with a confidence interval in the units the business cares about, then say whether that whole interval is worth acting on. A p-value only addresses whether you can rule out exactly zero; it says nothing about magnitude.

04

Solving silently instead of narrating the reasoning

Say which branch you are taking and why you chose it over the alternative, for example checking the denominator first because it changes what the comparison means. A correct answer that arrives with no visible path scores below a rigorous one that needed a hint.

Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.

9 technical prompts3 include a worked solution

Describe the process of feature engineering for a predictive model in …

medium
machine learning and modelling

Describe the process of feature engineering for a predictive model in a financial context.

Approach
  1. Set a baseline first, so any model has something honest to beat.
  2. Frame the prediction: the label, the moment of prediction, and the action it triggers.
  3. Pick an evaluation metric that matches the cost of each error type, not a default.
Follow-up
  • How would you choose the decision threshold, and who owns that choice?
  • Where could label leakage enter this setup?

Explain the trade-offs between different classification algorithms whe…

medium
machine learning and modelling

Explain the trade-offs between different classification algorithms when dealing with imbalanced datasets.

Approach
  1. Check what information would not exist at prediction time, and exclude it.
  2. Pick an evaluation metric that matches the cost of each error type, not a default.
  3. Say how the offline result would be validated online before it is trusted.
Follow-up
  • Where could label leakage enter this setup?
  • What would you monitor after launch to know the model is still valid?

Bootstrap a fraud loss rate that clusters within merchant

mediumWorked solution
bootstrapclustered resamplingheavy tails

You have a per-transaction frame with auth_id, merchant_id, settled_amount_reporting and net_loss_reporting, both already in one reporting currency. Most rows carry zero loss, a few carry large ones, and losses cluster within merchant. Using only numpy's random generator and no resampling helper from any library, write a bootstrap that returns a 95 percent interval for net fraud loss in basis points of settled volume, resampling merchants with replacement and taking all rows belonging to each drawn merchant. Also produce the naive row-level interval and state which you would report.

Approach
  1. State the estimator before writing it: total net loss divided by total settled volume, times 10,000. It is a ratio of sums, so each replicate recomputes both sums. Averaging per-transaction loss rates instead would weight a five-unit transaction like a five-thousand-unit one.
  2. Pre-aggregate loss and volume to merchant level once. For a ratio of sums, drawing merchants and taking all their rows is arithmetically identical to drawing merchant-level (loss_sum, volume_sum) pairs, so a replicate becomes one integer draw plus two vectorised sums rather than a groupby inside the loop.
  3. Draw B replicates of M merchant indices with replacement, where M is the observed merchant count, compute the ratio per replicate, and take the 2.5th and 97.5th percentiles. Say explicitly that this is a percentile interval and that BCa would correct the skew-induced bias if the decision is close.
  4. Repeat with independent row draws for the naive interval and compare widths on the same replicate count.
  5. Report the clustered interval. Rows within a merchant share an acceptance profile, a category code and a fraud exposure, so they are not independent, and the row-level interval understates variance by roughly the design effect.
Worked solution 30 min
  1. Compute the point estimate directly on the full data and keep it for comparison.
  2. Aggregate to merchant-level loss and volume arrays, record M, and set B to 2,000 with a seeded numpy Generator.
  3. In a vectorised loop, draw integer indices of shape (B, M), index both arrays, sum along axis 1, and take the ratio times 10,000.
  4. Repeat for the row-level version using the per-transaction arrays and N draws.
  5. Take the 2.5 and 97.5 percentiles of each replicate array and report both intervals alongside the point estimate.
EXPECTED RESULTTwo intervals in basis points sharing the same point estimate. The clustered interval is materially wider, commonly two to four times, and is right-skewed because a heavy merchant can be drawn more than once in a replicate.
Follow-up
  • Your clustered interval is three times wider. How do you explain that to someone who wanted a tighter number?
  • One merchant accounts for 40 percent of losses. What does that do to the interval, and what would you do about it?
  • How does this change if the question is whether two months differ rather than what this month's rate is?

Roughly 90 minutes a night on weekdays with one longer weekend block. The plan deliberately cuts scope rather than compressing everything, on the assumption that finishing one thing a night beats half-starting four.

Small steps. Visible outcomes.0 / 7 completed
ONE WEEK · YOUR PACE

Prepare, practise & reflect

One practical outcome each day. Spend longer where you need it.

0 / 7 done
01Fix the scope and set a baseline
  • Read the role description and write the three things the loop will almost certainly test, then write an explicit not-doing list for everything else and keep it visible all week.
  • Take one 20-minute SQL prompt and one 10-minute metric question cold, and write the single sentence that says what blocked each attempt, since that sentence is what decides which two topics get the most evenings.
  • Set the week's one rule: one problem finished to completion every night, including the night you only have 40 minutes.

Deliverable: A one-page scope with an explicit not-doing list and two cold attempts, each carrying one sentence on what blocked it.

Practice prompt ↗Practice prompt ↗Worked solution ↗
02One query pattern, written three times
  • Choose the single pattern most likely to appear (a cohort retention grid, or a funnel counted by user) and write it three times from a blank file rather than editing the previous attempt.
  • On the third attempt, write the grain of every CTE as a comment before writing its body.
  • Stop at 90 minutes even if the third version is imperfect, and write the one thing you would fix with another hour.

Deliverable: Three independent versions of the same query plus a note on what changed between them.

Practice prompt ↗Practice prompt ↗
03Only the statistics you will be asked to defend
  • Write, in under 200 words, how you would decide whether a difference between two groups is real: the test, its assumptions, and what you would switch to when an assumption fails.
  • Compute a 95 percent confidence interval for a difference in proportions by hand on realistic numbers, then write in one sentence what changes if the two samples are paired rather than independent.
  • Write your answer to "what does a p-value mean", check it against a definition, and delete the version that describes it as the probability the hypothesis is true.

Deliverable: A 200-word written answer and one hand-computed interval you can reproduce under pressure.

Practice prompt ↗Practice prompt ↗
04One case, and the assumptions holding it up
  • Answer one product case aloud in 20 minutes with a recording running, then listen back with a pen and mark every claim you asserted without saying what it rested on: an assumed user behaviour, an assumed data source, an assumed baseline rate, an assumed grain.
  • Pick the three assumptions the recommendation actually depends on, write how you would check each one against data, and say which one being wrong would flip the recommendation rather than merely weaken it.
  • Write the four-step structure you used onto a card small enough to hold in working memory when you are nervous.

Deliverable: One recording, three load-bearing assumptions each with a written check, and a four-step structure card.

Practice prompt ↗Practice prompt ↗Worked solution ↗
05Your own work, timed
  • Write a 90-second version and a four-minute version of your main project, and time both out loud rather than reading them.
  • Prepare answers to the two follow-ups that always come: what you would do differently, and how you knew it worked.
  • Put one number in the first sentence and be able to say exactly where that number came from and what it excludes.

Deliverable: Two timed narratives with one defensible number in the opening line.

Practice prompt ↗Practice prompt ↗
06The one full rehearsal, in a longer weekend block
  • Run a 60-minute mock covering query work, a case and a behavioural question in a single sitting with no breaks, because sustained attention is the thing evenings have not trained.
  • Immediately afterwards, and before hearing any feedback, write the three moments you lost the thread.
  • Spend the rest of the block only on those three moments, and on nothing you merely feel shaky about.

Deliverable: Mock notes naming three failure moments with a specific fix written under each.

Practice prompt ↗
07Taper
  • Write the 20-minute warm-up you will actually do on the morning of the interview: one query you can already write from a blank file, one metric you can define out loud, and nothing you have never seen before.
  • Re-read only your own notes from this week, and open no new material.
  • Write down the logistics: the tool you will be asked to work in, whether lookups are allowed, and the sentence you will use when you do not know something.

Deliverable: A one-page card holding the case structure, the project numbers, and the logistics.

Practice prompt ↗Worked solution ↗

Expand any day for tasks and deliverables. Your progress is saved on this device.

Nearly every data role forces a trade between the analysis you want and the one that fits the decision window. Prepare a case where you deliberately shipped something less rigorous, named the weakness to the person relying on it, and said what would change your answer. The naming is the part interviewers listen for.

How do you handle missing or noisy data in a production environment?

medium
behavioural and stakeholder questions

How do you handle missing or noisy data in a production environment?

Approach
  1. Close with what you would do differently, concretely.
  2. State the situation in two sentences and spend the rest on your reasoning.
  3. Quantify the outcome, including what you would not claim credit for.
Follow-up
  • How did you know the outcome was caused by your change?
  • What would you do differently if you ran that project again?

State honestly what your cutoff change actually contributed

hard
impact attributionswap setcounterfactual

Six months ago your recommendation moved a credit cutoff, using fct_loan_application and fct_loan_performance_monthly. Since then approval rate rose four points and the 12-month vintage 90-plus rate on affected cohorts is flat. In the same window the bureau changed a score attribute, marketing shifted channel mix toward broker, and the internal funding rate moved. Your performance review asks for impact in currency terms. Give the number you would stand behind, the counterfactual it rests on, and the part of the observed movement you would not claim.

Approach
  1. Define the counterfactual before computing anything: the claim is not what happened after the change, it is what would have happened had the old cutoff scored the same applications, which means replaying the old threshold on the post-change population.
  2. Build the swap set: applications the new cutoff approves that the old one declined, applications the old one approved that the new one declines, and everyone else held out as unaffected. Only the swap groups carry your effect. Note that the swap-out group has no outcome under the new rule, because those loans were never funded, so its forgone margin must be estimated from matched pre-change approvals rather than observed.
  3. Price each swap group at months_on_book equal to 12 on the measure the cutoff was meant to move: interest and fees collected, minus net charge-offs, minus funding cost at the internal transfer rate.
  4. Strip the confounders explicitly. Cohorts affected by the bureau attribute change are either recomputed on the old attribute or excluded; channel mix is held fixed by reweighting to the pre-change mix; funding cost is charged at the rate in force each month rather than one blended average.
  5. State the residual you will not claim, with its size, and give a range rather than a point wherever cohorts have not yet reached 12 months on book.
Follow-up
  • The swap-in group is only 6 percent of applications. How does that change the way you present the number, and to whom?
  • What would you have needed to set up at launch to make this attribution clean, and why was a randomised band around the cutoff not used?

Explain an incomplete dispute chart to a non-technical executive

easy
dispute maturitystakeholder communicationright-censoring

A finance lead is looking at first-chargeback rate by transaction month, built from fct_card_dispute joined to fct_payment_authorization on auth_id and attributed to requested_at. The last three months slope sharply down and the lead wants to announce a fraud improvement at tomorrow's review. Consumer dispute rights commonly run around 120 days from the transaction or expected delivery date, so those months are not complete. In five minutes, with no statistics vocabulary, explain why the decline is not yet evidence and say exactly what you would put on the slide instead.

Approach
  1. Lead with the mechanism in the listener's own terms, not with the statistical name for it: a dispute is attributed to the month the transaction happened, but it can be filed up to roughly 120 days later, so recent months contain only the disputes filed so far.
  2. Show completeness rather than arguing about the rate: for each transaction month, plot the share of its eventual disputes already filed, estimated from months that are fully matured. The last three months will sit visibly below 100 percent.
  3. Replace the chart with two artefacts: a matured series that stops 120 days back and is labelled final, and a development-factor estimate for the immature months drawn as a dashed range and labelled an estimate.
  4. Hand over one sentence the executive can repeat without you in the room: the recent months look better because the disputes have not arrived yet, not because fewer will arrive.
  5. Offer a weekly signal they can watch instead, such as the risk-score mix of approved volume or the decline-rule hit rate, and state up front what it does and does not predict.
Follow-up
  • The deck ships tomorrow regardless. What exactly goes on the slide, and what wording do you insist on?
  • How would you estimate the development factors, and how would you notice if they had shifted?
  • 01

    How do you handle missing or noisy data in a production environment?

  • 02

    Six months ago your recommendation moved a credit cutoff, using fct_loan_application and fct_loan_performance_monthly. Since then approval rate rose four points and the 12-month vintage 90-plus rate on affected cohorts is flat. In the same window the bureau changed a score attribute, marketing shifted channel mix toward broker, and the internal funding rate moved. Your performance review asks for impact in currency terms. Give the number you would stand behind, the counterfactual it rests on, and the part of the observed movement you would not claim.

  • 03

    A finance lead is looking at first-chargeback rate by transaction month, built from fct_card_dispute joined to fct_payment_authorization on auth_id and attributed to requested_at. The last three months slope sharply down and the lead wants to announce a fraud improvement at tomorrow's review. Consumer dispute rights commonly run around 120 days from the transaction or expected delivery date, so those months are not complete. In five minutes, with no statistics vocabulary, explain why the decline is not yet evidence and say exactly what you would put on the slide instead.

PracHub interview preparation framework
Is this an official Dave interview guide?

No. It is PracHub's own research and practice material for the Data Scientist role at Dave. Rounds and questions reflect what candidates have reported, not a process Dave has published, and they change over time. Confirm the current format and scope with your recruiter.

PracHub interview research
How long does the interview process usually take?

The process is generally fast, often moving from the initial screen to an offer in under one month.

PracHub interview research
What is the difficulty level of the coding portion?

The coding interviews are typically of average difficulty, focusing on practical data manipulation and common algorithmic patterns rather than obscure competitive programming puzzles.

PracHub interview research
How should I prepare for the case study?

Focus on the 'why' and 'how' of your approach. Structure your answers by defining the problem, outlining your assumptions, proposing a solution, and discussing how you would measure success.

PracHub interview research
Does Dave value experience in specific industries?

While fintech experience is a plus, the team values strong analytical fundamentals and the ability to learn quickly above specific domain expertise.

PracHub interview research
Sources & methodology 3 sources ↗

Official role evidence, timestamped platform data and clearly labeled preparation advice.