The design doc says medallion, mesh and Lambda. What do you ask?
Whether the candidate can tell a naming convention from an architecture, an organisational model from a technical one, and can price each before adopting it.
The situation behind the question
Interviewers ask this because it happened to them.
A proposal for a new platform specifies bronze, silver and gold layers, a data mesh organisational model, and a Lambda architecture with parallel batch and streaming paths. The company has three product teams and one data engineer.
A strong answer
Flags
Green flags
- Asks which requirement forces each component, and is comfortable removing the ones with no answer.
- Knows medallion is a convention and can state what actually justifies a layer.
- Treats mesh as an organisational investment with a staffing plan, not as a diagram.
- Does not choose streaming without a consumer latency requirement, and can say what the second implementation costs.
Red flags
- "Streaming is always better than batch." Freshness has a price in state, ordering, lateness policy and incident duration, and it is worth paying only where it is needed.
- Adopts a layering convention as a requirement without being able to say what each layer is for.
- Presents mesh as an architecture rather than as an operating model with real cost.
- Presents Lambda or Kappa as simpler in general, rather than simpler for a specific set of consumers.
Follow-ups
Where the conversation goes if the first answer holds up.
- Which of the three would you keep for this company, and what would have to change for the others to become right?
- What does the second implementation in Lambda actually cost you over a year?
- If you adopted mesh anyway, what is the first thing that would go wrong?