The Firehose and the Ledger
A hard Pipeline Design mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.
- Domain
- Pipeline Design
- Difficulty
- hard
- Seniority
- senior
Interview Prompt
We ingest payment events from a few hundred partner APIs, some pushing webhooks and some we poll on a schedule, totaling around 2 billion events a day. Operations needs a near-real-time view of transaction volume and error rates within seconds, while finance needs an exactly-once daily ledger that reconciles to the cent. Partners go down and resend the same events when they recover, so the platform has to retry, deduplicate, and never lose or double-count a transaction.
How This Interview Works
- Read the vague prompt (just like a real interview)
- Ask clarifying questions to the AI interviewer
- Write your pipeline design solution with real code execution
- Get instant feedback and a hire/no-hire decision