Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Ola hiring for Data Analytics roles
Ola, operated by ANI Technologies, is an Indian ride-hailing platform offering cabs, auto-rickshaws and bike taxis, and it is part of a group that also includes Ola Electric and Krutrim. Its technology and analytics teams work on pricing, dispatch, maps and driver supply. It hires for software engineers, SDETs, business analysts and data scientists.
For Data Analytics roles, this Ola practice set focuses most on SQL (6), Statistics and Case Studies (6), Python for Analysis (5), Data Cleaning (5). It has 2 easy, 27 medium, 11 hard questions, so you can start easy and work up to the harder ones.
Company type
Product
Headquarters
Bengaluru, India
Main India offices
Bengaluru
Ola Data Analytics interview process
Online coding assessment
Technical round 1 (DSA)
Technical round 2 (design or case)
Hiring manager round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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01
What are additive, semi-additive and non-additive facts?
Additive facts, like sales amount or quantity, can be summed across every dimension. Semi-additive facts, like account balance or stock on hand, can be summed across accounts or stores but not across time; for time you take the closing or average value. Non-additive facts, like percentages, ratios or unit prices, cannot be summed at all, so you store their components (profit and revenue) and calculate the ratio at query time.
IN checks whether a value is in a list or subquery result; EXISTS checks whether a subquery returns at least one row and stops at the first match. Results are the same in most cases, and modern optimisers often run them similarly. The big difference is NOT IN with NULLs: if the subquery returns any NULL, NOT IN returns no rows. NOT EXISTS behaves correctly, so prefer it for anti-joins.
A dataflow is Power Query running in the Power BI Service. It extracts and cleans data once and stores the result so many datasets can reuse it. For example, a single cleaned Customer table can feed sales, finance and marketing reports, ensuring consistent logic and reducing load on the source. Dataflows suit shared, reusable preparation; logic that only one report needs can stay in that report's Power Query.
05
Orders arrive in the warehouse with customer IDs that do not exist yet in the customer dimension. What do you do?
These are late-arriving dimensions. Do not drop the orders, or revenue will be understated. Common practice is to insert a placeholder customer row with the natural key and 'Unknown' attributes, link the order to it, and update that row when full details arrive. Alternatively map to a single Unknown member with key -1. Also monitor how many such rows appear daily, because a spike usually means a broken feed.
06
Write SQL to calculate monthly customer churn rate.
WITH active AS (
SELECT DISTINCT customer_id,
DATE_TRUNC('month', order_date) AS month
FROM orders
)
SELECT a.month,
COUNT(*) AS active_customers,
COUNT(*) - COUNT(n.customer_id) AS churned_next_month,
ROUND(100.0 * (COUNT(*) - COUNT(n.customer_id)) / COUNT(*), 1) AS churn_pct
FROM active a
LEFT JOIN active n
ON n.customer_id = a.customer_id
AND n.month = a.month + INTERVAL '1 month'
GROUP BY a.month
ORDER BY a.month;
07
Your 50/50 test has 52,400 users in control and 47,600 in treatment. What does this tell you?
This is a sample ratio mismatch. A chi-square test on these counts gives a tiny p-value, so the gap is not chance. Something is filtering users unevenly, such as the treatment page crashing on some devices, a redirect losing tracking, bots in one arm or a bug in assignment. The results cannot be trusted until the cause is found. Check splits by browser, platform and day to locate it.
08
A retail chain asks you which of its 120 stores it should close. How do you approach it?
Clarify the goal first: profit, cash or market share. Build a store-level dataset with revenue, contribution margin after rent and staff, trend over 24 months, footfall, catchment demographics and cannibalisation with nearby stores. Separate structural losers from stores that are new or temporarily disrupted. Estimate how much revenue would shift to nearby stores or online if a store closes. Present a shortlist with scenarios and risks, not a single answer.
Read the execution plan, add or fix indexes, select only needed columns, filter early, avoid functions on indexed columns, and replace correlated subqueries with joins.
10
Your Top 10 products filter in Tableau ignores the category filter. Why, and how do you fix it?
A context filter is applied before other dimension filters and before FIXED LOD calculations, creating a smaller dataset the rest of the view works on. Use it when a Top N filter should operate within a selected category, for example top 10 products within Electronics, or when a FIXED LOD must respect a filter. Add a filter to context from its right-click menu; it turns grey. Too many context filters can hurt performance.
// First Purchase Date
{ FIXED [Customer ID] : MIN([Order Date]) }
// Order Type
IF [Order Date] = [First Purchase Date]
THEN 'New'
ELSE 'Repeat'
END
// Cohort Month for retention analysis
DATETRUNC('month', [First Purchase Date])
14
Write Python code to calculate the sample size per group for a conversion test with a 4% baseline and a 10% relative lift.
# Fill missing delivery_days with the median for that city
df['delivery_days'] = (
df['delivery_days']
.fillna(df.groupby('city')['delivery_days'].transform('median'))
)
# Rows in a city with no values at all stay NaN; fall back to overall median
df['delivery_days'] = df['delivery_days'].fillna(df['delivery_days'].median())
17
A senior stakeholder insists the data supports their conclusion, but your analysis does not. How do you handle it?
Stay respectful and focus on evidence, not opinions. Ask what they are seeing that leads to their view, as they may know context you lack. Walk through your method transparently, show the specific numbers, and test their hypothesis together on a cut they suggest. If the data still disagrees, present both views with their assumptions to the decision maker. Never adjust the analysis to fit a preferred answer.
18
You must present to the sales team that they missed their quarterly target by 18%. How do you handle it?
Lead with the fact clearly, then show where the gap came from, such as which regions, products or deal stages, so it becomes actionable rather than a blame session. Separate controllable causes like lower conversion from uncontrollable ones like a delayed product launch. Highlight what did work, and end with two or three specific actions and the metrics to track them. Share the numbers with sales leaders privately first, to avoid surprises.
19
How do you calculate a simple customer lifetime value?
A simple formula is CLV = average order value x purchase frequency per year x gross margin x expected lifetime in years. Example: 800 rupees x 6 orders x 30 percent margin x 3 years = 4,320 rupees. Expected lifetime can be estimated as 1 divided by annual churn rate. A better version discounts future value and calculates CLV by cohort or segment, because averages hide very different customer groups.
20
What is the difference between dimensions and measures in Tableau?
Dimensions are qualitative fields such as region, product or date that slice data into groups and create headers. Measures are quantitative fields such as sales or profit that get aggregated, by default with SUM. Dragging a dimension to rows creates one row per member; dragging a measure creates an axis. A numeric field like customer ID should be converted to a dimension so it is not summed.
21
The CMO asks which marketing channel should lose 20% of its budget. How do you approach it?
I would compare channels on incremental return, not last-click ROAS. Gather spend, attributed conversions under two models, customer quality such as repeat rate and margin, and any lift test or mix model results. Look at diminishing returns: the last rupee in a saturated channel is worth less than the average. Then recommend cutting where marginal return is lowest, ideally phased with a holdout to confirm the impact.
22
How do you handle large CSV files that do not fit in memory in Python?
Broadcasting lets NumPy perform operations on arrays of different shapes without copying data, by virtually stretching the smaller array. For example, subtracting a 1D array of column means from a 2D array centres every column in one line: X - X.mean(axis=0). Shapes are compatible when trailing dimensions are equal or one of them is 1. It is a key reason vectorised code is much faster than Python loops.
25
What is the difference between mean and median for reporting salaries?
-- Works in PostgreSQL, Snowflake, SQL Server (with OVER for SQL Server)
SELECT
city,
PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY order_value) AS median_value,
AVG(order_value) AS mean_value
FROM orders
GROUP BY city
ORDER BY median_value DESC;
27
How do you remove duplicates in Excel but keep the latest record?
Sort by date (newest first), then Data → Remove Duplicates on the key column — Excel keeps the first occurrence. Or use UNIQUE / a COUNTIFS helper column.
28
Organic search traffic fell 40% overnight. How do you investigate?
First check whether it is a tracking problem: did the analytics tag break on some templates, did consent settings change, does server log or backend order data show the same fall? If the drop is real, check the search console for impressions and rankings, recent site releases such as changed URLs, missing redirects, noindex tags or robots.txt changes, and whether a search algorithm update or seasonal pattern matches. Then break the drop down by page group.
29
What is the difference between a table and a normal range?
SELECT customer_id,
CASE WHEN email IS NULL OR email NOT LIKE '%_@_%._%' THEN 1 ELSE 0 END AS bad_email,
CASE WHEN LENGTH(pincode) <> 6 THEN 1 ELSE 0 END AS bad_pincode,
CASE WHEN signup_date > CURRENT_DATE THEN 1 ELSE 0 END AS future_signup,
CASE WHEN age NOT BETWEEN 18 AND 100 THEN 1 ELSE 0 END AS bad_age
FROM customers;
-- sum each flag to report the error rate per rule
32
An inner join between orders and customers returns fewer orders than the orders table has. What could be wrong?
Orphan records are child rows whose foreign key has no matching parent, such as orders with a customer_id that does not exist in the customer table. They break joins silently: an inner join drops them and totals fall short. Find them with a LEFT JOIN from the child to the parent and filter where the parent key IS NULL. Then fix the source, add an Unknown member, or report them separately.
33
Write SQL using LAG to compare each month's revenue with the previous month.
WITH monthly AS (
SELECT DATE_TRUNC('month', order_date) AS month,
SUM(amount) AS revenue
FROM orders
GROUP BY 1
)
SELECT month,
revenue,
LAG(revenue) OVER (ORDER BY month) AS prev_revenue,
ROUND(100.0 * (revenue - LAG(revenue) OVER (ORDER BY month))
/ NULLIF(LAG(revenue) OVER (ORDER BY month), 0), 1) AS mom_pct
FROM monthly
ORDER BY month;
34
Average delivery time improved by 4 minutes, but customer complaints about late deliveries went up. How do you investigate?
An average can improve while the tail gets worse. I would look at the distribution: median, 90th and 95th percentiles and the share of orders beyond the promised time. Then break it down by city, time slot and restaurant to see where late orders cluster. Also check whether promised times changed, whether complaint tracking changed and whether a few very fast orders pulled the mean down.
35
How do you measure impact when a proper A/B test is not possible?
Use quasi-experimental methods. Difference-in-differences compares the change in a treated group, such as cities that got a new policy, with the change in similar untreated cities over the same period. Synthetic control builds a weighted mix of untreated regions to mimic the treated one. Regression discontinuity uses a cut-off, like a credit score threshold. Always check pre-period trends and state the assumptions clearly.
A calculated column is computed row by row and stored in the model. A measure is computed at query time using the filter context, e.g. Total Sales = SUM(Sales[Amount]). Prefer measures for aggregations.
37
Find customers who ordered in January but not in February.
This is an encoding mismatch: a UTF-8 file was read as a different encoding such as Latin-1 or Windows-1252. Re-read it with the right encoding, for example pd.read_csv(path, encoding='utf-8') or 'utf-8-sig' for files with a byte order mark, or set the file origin in Excel and Power Query import. Avoid re-saving through tools that change encoding, and agree on UTF-8 for all exchanges, especially for Hindi or other Indian language text.
39
Write pandas code to compute month-on-month percentage change and cumulative sales for each store.
df = df.sort_values(['store', 'month'])
df['mom_pct'] = (
df.groupby('store')['sales'].pct_change() * 100
).round(1)
df['cum_sales'] = df.groupby('store')['sales'].cumsum()
# first month of each store has NaN for mom_pct, which is expected
MCAR, missing completely at random, means missingness is unrelated to anything, like a random sensor glitch; dropping rows is mostly safe. MAR, missing at random, means missingness depends on other observed variables, for example older customers skipping the email field; impute using those variables. MNAR, missing not at random, means it depends on the missing value itself, like high earners hiding income; this biases results and needs careful handling or extra data.
Tips to crack the Ola Data Analytics interview
Prepare marketplace cases on driver supply, rider demand and surge pricing in Indian cities.
Practise DSA problems on graphs and heaps, which relate to dispatch and route optimisation.
Read about Ola Maps and Krutrim AI efforts, which are recent technology focus areas for the group.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; Ola interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Ola Data Analytics interview?
Candidates usually go through 4 stages: Online coding assessment; Technical round 1 (DSA); Technical round 2 (design or case); Hiring manager round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the Ola Data Analytics interview?
This practice set leans on SQL (6), Statistics and Case Studies (6), Python for Analysis (5), Data Cleaning (5). Revise those first, then practise explaining one or two of your own projects end to end, because most Ola interviewers ask you to walk through real work.
Are these the exact questions asked at Ola?
No. These are curated practice questions that match the skills and difficulty usually tested in product interviews like Ola's. They are not a leaked or verified list of past questions.
Where does Ola hire Data Analytics professionals in India?
Ola has large teams in Bengaluru. Openings and locations change often, so check the Ola careers page and filter by city and experience.