A New Column on a Billion Rows
A hard Pipeline Design mock interview question on DataDriven, with an AI interviewer who asks follow-up questions and a hire or no-hire decision at the end.
- Domain
- Pipeline Design
- Difficulty
- hard
- Seniority
- L6
Interview Prompt
Our orders table holds a billion rows and takes 50K writes a minute, and both analytics replicas and the change-data-capture feed that loads our warehouse read from it. Design how we add a new column and fill it for every existing row within a week, knowing the next app release starts setting the column on every write.
Summary
Add and backfill a new column to a billion-row production table with zero downtime.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Draw your pipeline on the design canvas: sources, transforms, storage and checks
- Answer the interviewer's follow-up questions, then get a hire or no-hire decision