Forward Deployed Engineer Interview Guide: Coding, Decomposition and Customer Rounds

Every company runs its own process, but FDE interviews usually test two things at once: can you build, and can you work with a customer? Prep guides and candidate reports describe a loop with the rounds below. Treat it as a pattern, not a promise, and check the exact steps with the recruiter.

The usual loop

Round	What it tests
Recruiter screen	Motivation, background, why this role
Technical / coding	Practical coding, APIs, data handling and debugging
Decomposition (system)	Turning a vague business goal into a buildable plan
Customer scenario	Talking to a "customer" played by the interviewer
Behavioural / ownership	How you handled ambiguity, conflict and failure

Some companies add a take-home or live build. Candidate guides report that a decomposition round at some firms, for example Databricks, runs about an hour. Details change, so verify.

Round 1: technical

Expect less puzzle-style work and more realistic tasks: call an API and process the response, clean a messy dataset, write SQL for a business question, or debug a failing script. Practise with the DSA plan, SQL practice and online assessment tips. Talk through your thinking, and handle errors and edge cases.

Round 2: decomposition

You get a vague goal such as "a logistics company wants to reduce late deliveries using AI." There is no single right answer. The interviewer watches how you think.

A method you can reuse:

1. Clarify the goal. Who is the user? What decision or task changes? What does success look like in numbers?
2. Ask about the data and systems. What data exists, where, how clean, who owns it, what is sensitive?
3. Understand the current process. Walk it step by step and find the painful one.
4. Define constraints. Time, budget, security, compliance and who must approve.
5. Pick a first slice. The smallest version that proves value in weeks.
6. Sketch the system. Inputs, processing, outputs, human review, monitoring.
7. List risks. Bad data, wrong outputs, adoption, cost, and how you would measure and reduce each.
8. Plan rollout. Pilot with one team, measure, then expand.

What interviewers dislike: jumping straight to a solution, never asking questions, building an over-complicated system, and ignoring the people who must use it.

Round 3: customer scenario

The interviewer plays a customer who may be busy, unclear or sceptical. Show that you can:

• Open with a short summary of what you understood, and confirm it
• Ask questions before proposing anything
• Explain trade-offs without jargon
• Say "I don't know yet, here is how I would find out"
• Push back politely when the request is unrealistic
• Close with next steps, an owner and a date

Round 4: behavioural

Prepare real stories with the STAR method: a vague project you scoped, a time you disagreed with a stakeholder, something that failed in production, and a time you learned a new tool quickly.

Sample questions

• Walk me through a project where requirements kept changing. What did you do?
• A customer says the AI answers are "wrong sometimes." How do you investigate?
• How would you decide between building a custom feature and asking the product team?
• Design a system to extract data from thousands of invoices for a finance team.
• How do you explain a model's limits to a non-technical manager?
• What would you do in your first two weeks inside a customer's team?
• Tell me about a time you shipped something imperfect on purpose.

A four-week preparation plan

Week	Focus
1	Coding and SQL practice on realistic tasks. Review APIs and HTTP
2	Practise the decomposition method on five different business problems, out loud
3	Role-play customer scenarios with a friend. Prepare six STAR stories
4	Mock full loops. Review your portfolio so you can defend every choice

Final tips

• Think aloud, and write a short plan before you start.
• Tie every answer to customer outcome, not only technology.
• Ask good questions at the end. See questions to ask the interviewer.
• For general preparation, use the technical interview checklist.

Further reading

• The FDE interview loop (Exponent)