You have inherited four teams each running their own ingestion pipeline and their own warehouse. Leadership wants one data platform. How do you design it, and how do you get there?
What they are really testing: Whether you can design a target architecture and a migration path that respects existing teams, instead of proposing a rewrite that never lands.
A real interview question
You have inherited four teams each running their own ingestion pipeline and their own warehouse. Leadership wants one data platform. How do you design it, and how do you get there?
What most people say
drag me
“I would pick the best of the four platforms, standardise everyone onto it, and decommission the others within a quarter.”
It is a mandate, not a design. It ignores that each pipeline encodes years of business logic, and quarter long big bang migrations across four teams almost never land intact.
The follow-ups they ask next
One team refuses to migrate. What do you do?
Do not escalate first. Find why, usually a real constraint. Then make the platform strictly better for them and let cost transparency do the arguing.
How do you know the migrated pipeline produces the same numbers?
Dual run with automated reconciliation on agreed key metrics and a tolerance threshold, for a fixed window, before the old pipeline is turned off.
Leadership wants this done in one quarter. How do you respond?
Show the sequencing and what one quarter actually buys, then offer the one visible win that fits, rather than agreeing and missing.
What the interviewer is listening for
- Quantifies the current cost and the duplicated effort before designing anything
- Separates platform ownership from data ownership
- Proposes an incremental strangler migration with a parity check
- Uses cost transparency as the incentive rather than a mandate
What sinks the answer
- Proposes a big bang rewrite with a hard deadline
- Centralises all data ownership into one team and creates a bottleneck
- No plan to verify the new numbers match the old ones
- Ignores the organisational reality and treats it as purely a tooling choice
If you genuinely do not know
Say this instead of freezing. Reasoning out loud from what you do know beats silence every single time, and a good interviewer is listening for exactly that.
“I have not led a platform consolidation, but here is how I would reason about it. I would start by finding out what the duplication actually costs today, because that number is what buys me the time to migrate carefully.”
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