Eigenquestion

An Eigenquestion is the smallest set of questions whose answers determine the most important decisions in a problem space. The term borrows from linear algebra: an eigenvector is a vector that, when a transformation is applied, changes only in scale — not in direction. An Eigenquestion is the question that drives the answer rather than being driven by it.

The concept was named and popularised by Shishir Mehrotra, co-founder and CEO of Coda, who uses it as an interview question and as a product strategy tool.

The teleportation device exercise

Mehrotra’s canonical exercise: a group of scientists has invented a teleportation device and hired you to bring it to market. What do you do? Candidates typically generate a long list of clarifying questions. Then: “These scientists hate talking to people. They will answer only two of your questions, and after that they expect a plan. What two questions do you ask?”

The constraint forces the solver to find the Eigenquestions:

1. Is it safe enough for humans? (The safety threshold determines the entire class of use cases.)
2. Is it more expensive as CapEx (to buy) or OpEx (to run)? (The cost structure determines the deployment and pricing model.)

With just those two questions, a 2×2 emerges that maps to the major strategic options — airport replacement, human fax machines, goods transport only, and so on. The Eigenquestions unlock the rest without requiring more information.

Why Eigenquestions are rare

Most people in interviews (and strategy discussions) ask for information rather than for decisions. “What size is it?” is not an Eigenquestion — knowing the size does not automatically resolve any strategic decision. The discipline of Eigenquestion thinking is to filter every question through: “What decision does the answer to this question allow me to make that I could not make without it?”

Mehrotra notes that children are unusually good at this — they quickly reduce problems to their essential questions. The skill is learned out of people by years of structured problem-solving that reward thoroughness over precision.

Applications

Product strategy. Before launching a strategy exercise, identify the one or two questions whose answers would make the key decisions obvious. The rest of the strategy document fills in once those are answered.

Hiring. Mehrotra uses the exercise as an interview question not to test teleportation knowledge but to assess: can this person identify the question that drives the answer? Strong candidates find the Eigenquestions regardless of the domain.

Diagnosis and prioritisation. When a product or organisation has too many open questions, identifying the Eigenquestions reduces paralysis: answer those first; the rest become tractable.

In the wiki

• The Best Interview Questions from Lenny's Podcast (Compilation) — primary source; Shishir Mehrotra demonstrates the Eigenquestion methodology via the teleportation exercise