Order Transformer — Coding Assessment

A .NET 9 Worker Service that monitors Azure Blob Storage for incoming XML order files, transforms them to JSON, and stores the output back to blob storage.

Interview Plan

In this assessment you have tools:

• VS Code
• Claude Code
• Azure Storage Explorer
• Docker Desktop
• Terminal

Phase 1: Read and Explain (~15 minutes)

Goal: Candidate reads the codebase and demonstrates understanding by drawing and explaining.

1. Read the code — Start from Program.cs and trace the execution flow through the application
2. Draw the process — On the whiteboard, draw a diagram showing:
   • How the application starts and what triggers processing
   • The pipeline stages and what each service does
   • How data flows from XML input to JSON output
   • What happens to files after processing (success and failure paths)
3. Explain the architecture — Walk through the diagram and explain:
   • Why is each service behind an interface?
   • Why are models defined as records with init setters?
   • How does the pipeline handle validation errors — does it stop or continue?
   • What happens if one file fails — does it affect other files?

Phase 2: Design and Implement (~30 minutes)

Goal: Candidate receives a new feature requirement, designs the solution, then implements it.

1. Receive the requirement — Product Owner presents the new feature spec from specs/features/
2. Design first — Before writing any code:
   • Read the existing code to find where the change belongs
   • Draw the updated validation flow on the whiteboard
   • Explain the approach: what changes, what stays the same
   • Discuss edge cases and testing strategy
3. Create the spec — Write or update the feature spec with design decisions
4. Implement — Write the code:
   • Follow existing patterns in the codebase
   • Use AI tools (Copilot, Claude Code, etc.) — we want to see how you work with them
   • Run tests incrementally, not just at the end
5. Verify — Build, test, and run end-to-end with Docker

Start Services

# Start infrastructure
docker compose up -d

# Verify seed data
docker compose logs azurite-init

# Run tests (should all pass)
dotnet test tests/OrderTransformer.Tests

# Run the app
dotnet run --project src/OrderTransformer

Clean Up

docker compose --profile app down -v