The Interview Loop
Recruiter Screen (30 min)
Standard fit check, behavioral questions, and resume overview.
Technical Loop (3-4 Rounds)
Deep dive into domain knowledge, coding, and system design.
Interview Question Bank
Data Engineer
•
Coding
•
medium
Write a query to calculate the cumulative balance of a wallet address given a ledger of debit and credit transactions.
#SQL
#Window Functions
#Running Totals
Data Engineer
•
Coding
•
medium
Write a SQL query to find the 7-day rolling average of daily transaction volume per user.
#SQL
#Window Functions
#Time-series
Data Engineer
•
Coding
•
medium
Write a SQL query to identify 'whale' wallets that have transferred more than $1,000,000 in aggregate volume in a single calendar day.
#SQL
#Aggregations
#GROUP BY
Data Engineer
•
Coding
•
hard
Write a SQL query to find the maximum consecutive days a user has made at least one trade (trading streak).
#SQL
#Gaps and Islands
#Window Functions
Data Engineer
•
Coding
•
medium
Given a table of user logins and a table of trades, write a query to find the percentage of users who made a trade within 1 hour of logging in.
#SQL
#Joins
#Date Math
Data Engineer
•
Technical
•
medium
Calculate the Daily Active Users (DAU) and the month-over-month retention rate for the Coinbase Pro platform.
#Cohort Analysis
#Retention
#Aggregations
Data Engineer
•
Technical
•
medium
Given a table of order book snapshots (bids and asks), write a query to calculate the bid-ask spread for BTC-USD at the end of every hour.
#Window Functions
#Filtering
#Financial Data
Data Engineer
•
Technical
•
easy
Write a SQL query to find the first and last transaction timestamp, along with the respective amounts, for every wallet address.
#Aggregations
#Window Functions
Data Engineer
•
Technical
•
hard
How would you handle late-arriving blockchain transaction data in a daily aggregate table? Write a SQL MERGE statement to update the aggregates.
#Idempotency
#MERGE/UPSERT
#Data Warehousing
Data Engineer
•
Technical
•
medium
Write a query to identify users who made a fiat deposit but did not execute any crypto trades within 24 hours of that deposit.
#Left Joins
#Time Intervals
#Funnel Analysis
Data Engineer
•
Technical
•
medium
Write a SQL query to calculate the 7-day moving average of trading volume for each cryptocurrency asset on the platform.
#Window Functions
#Time Series
#Aggregations
Data Engineer
•
Technical
•
medium
Given a 'transactions' table, write a query to find the top 3 users by total transaction volume for each month.
#CTEs
#Ranking Functions
#Date Truncation
Data Engineer
•
Technical
•
hard
Write a SQL query to identify potential 'wash trading'—instances where a user buys and sells the same asset to themselves within a 1-minute window.
#Self Joins
#Time Intervals
#Fraud Detection
Data Engineer
•
Technical
•
hard
Given a table of user login and logout timestamps, write a query to find the maximum number of concurrent active user sessions on the exchange.
#Cumulative Sum
#Event Sourcing
#Advanced SQL
Machine Learning Engineer
•
Coding
•
easy
Write a SQL query to find the user with the highest total transaction volume in the last 30 days, excluding internal transfers.
#Joins
#Aggregations
#Filtering
Machine Learning Engineer
•
Coding
•
medium
Write a SQL query to calculate the 7-day rolling average trading volume for each cryptocurrency asset.
#Window Functions
#Aggregations
Machine Learning Engineer
•
Coding
•
medium
Write a SQL query to find all users who made more than 5 transactions within any rolling 10-minute window.
#Window Functions
#Time Series Data
Software Engineer
•
Technical
•
medium
Given a 'trades' table with columns (trade_id, user_id, amount, price, created_at), write a SQL query to find the top 5 users by total trading volume in USD over the last 7 days.
#SQL
#Aggregations
#Data Analysis
Difficulty Radar
Based on recent AI-sourced data.
Meet Your Interviewers
The "Standard" Interviewer
Senior EngineerFocuses on core competencies, system constraints, and clear communication.
SimulateUnwritten Rules
Think Out Loud
Always explain your thought process before writing code or drawing architecture.