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AI Product Strategy and Model Choice

Build vs Buy vs Fine-Tuning Decisions Interview Questions

When to use an API, when to buy a product and when fine-tuning is worth it: data needs, cost predictability, reversibility and lock in. A favourite question for AI PMs and a common system design discussion for AI engineers.

  • 23 questions with model answers
  • 2 foundational · 11 intermediate · 10 advanced

Foundational Build vs Buy vs Fine-Tuning Decisions Questions

  1. Lay out the decision tree for build, buy, prompt, retrieve or fine-tune.Concept
  2. What conditions make buying a vendor solution the right call for an AI feature?Concept

Intermediate Build vs Buy vs Fine-Tuning Decisions Questions

  1. Explain the strategic risk of building your core differentiator on a third-party model.Concept
  2. When does fine-tuning pay for itself relative to a better prompt?Concept
  3. What is the switching cost of a fine-tuned model versus a prompted one?Concept
  4. Explain when building your own retrieval layer beats using a managed one.Concept
  5. How does team capability change a build-versus-buy answer that is otherwise identical?Concept
  6. Your CFO wants predictable costs. How does that shape the build-buy-finetune choice?Case
  7. Compare time-to-market for the three paths on a feature you specify yourself.Case
  8. Explain the argument for buying now and building later, and its main failure mode.Concept
  9. Describe how vendor lock-in shows up in an AI stack specifically.Concept
  10. Structure the one-page recommendation memo for a build-versus-buy decision.Artifact critique
  11. Explain when the right answer is buy the platform and build the workflow on top.Concept

Advanced Build vs Buy vs Fine-Tuning Decisions Questions

  1. Your vendor's pricing changes annually. How does that affect a build-versus-buy analysis?Calculation
  2. Describe the total cost of ownership of a self-hosted open model versus an API.Calculation
  3. A vendor offers 90 percent of what you need. How do you evaluate closing the last 10 percent yourself?Case
  4. Describe the reversibility test you would apply to this decision.Concept
  5. What data volume and quality do you need before fine-tuning is even worth considering?Concept
  6. When does building become a hiring decision rather than an engineering decision?Concept
  7. What would make you reverse a build decision six months in?Case
  8. How do you factor in that the buy option's capability improves without your effort?Concept
  9. Your competitor built; you bought. How do you assess whether that was a mistake?Case
  10. Walk me through a build-versus-buy decision you would make for a company I name.Interview

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