My Favorite Product Discovery Tool: Assumption Mapping
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My Favorite Product Discovery Tool: Assumption Mapping<br>A simple technique that generates a ton of insight and can redraw the roadmap before we even start building.
Pawel Brodzinski<br>Jul 08, 2026
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At Lunar Logic, we often start working with founders who are still at the pre-development stage. We typically get them through the discovery phase before we commit to building anything. Every other time, it ends with abandoning the development.<br>One pivotal part of any discovery workshop we run is assumption mapping. It’s also my favorite part. The reason is simple. No matter how much the founders claim they verified their idea, we always uncover new, interesting stuff. “Interesting,” as in: if not true, then the whole business doesn’t make sense, and we can find evidence whether it’s true or not.
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Assumption Mapping: The Basics
Assumption mapping originates from Lean UX and was popularized by David Bland. It starts with considering the idea from three aspects: desirability, viability, and feasibility. Each answers a different question.
Desirability covers whether people want a specific solution. It is front and center when we consider problem-solution fit.
Viability answers whether we can build a sustainable business around the idea. It is a focal point when we search for product-market fit.
Feasibility is all about whether we can technically build the thing. Depending on the idea, it may be the critical or largely ignored part. Or anything in between.
For each of the trio, we brainstorm statements following the pattern: “We believe that...” For desirability, it would be variations of saying that we believe people would want the thing. For viability, different ways of stating that people would pay for it. Etc.<br>These are our assumptions. Note, they should be specific and narrower than “we believe that people will want our thing and will pay for it.” Also, brainstorming means generating ideas beyond the usual suspects. Finding non-obvious beliefs is the whole point of the activity.<br>“What gets us into trouble is not what we don’t know. It’s what we know for sure that just ain’t so.”<br>Mark Twain
The biggest risks for a startup are not the things that instantly come up when a founder is asked about them. It’s what’s below the radar. Stuff that we subconsciously assume must work, while reality might have other plans for us.<br>That’s where the last part of assumption mapping kicks in. We sort the ideas using a two-dimensional space. One axis is evidence. If we already have a lot of data that backs up the belief, the item goes one way. If we don’t have the data, it goes the other. I like to frame it as the uncertainty axis.<br>The second dimension is importance understood as “How fucked up would we be if this thing ain’t true?” The axis goes from “whatever” to “we’re toast.” Think of it as Mark-Twain-o-Meter.
Once you’re done sorting, you’re looking at the priorities for your exploration. Whichever items end high on both the uncertainty scale (no data to support the assumption) and Twain-o-Meter (we’re toast if it ain’t true) are the first to be validated.<br>Hiring Is Broken or a Practical Example of Assumption Mapping
Let’s take one idea that we’ve recently worked with. The underlying observation is simple. Hiring is broken. AI has removed the remaining ways to convey care between a candidate and a hiring company, or vice versa. It’s increasingly a game between one AI agent (mass-sending generated resumes) and another (filtering out 95% of applications before any human can even see it). Can we create an experience for both candidates and hiring companies that would sidestep this reality altogether?<br>It would be a service where a candidate can send a “I genuinely care about this particular job” signal. A hiring company, in turn, would be inclined to get such an application directly to a human recruiter, bypassing the AI filtering plumbing. In other words, if there was such a marketplace, both parties would (hypothetically) benefit.<br>So let’s look at some examples of assumptions behind this idea.<br>Desirability
Desirability considers whether people want a specific product, solution, or offering. Again, think in terms of problem-solution fit. Sample beliefs will thus be as follows:<br>We believe that job seekers genuinely care about some jobs much more than others.
We believe that job seekers would attach a “token of care” to an application for a job they care about, given the chance.
We believe that hiring companies would prioritize applications from candidates who care about the job over an average submission.
We believe that, in the current hiring landscape, candidates have lost an opportunity to convey information that they care about a particular job.
Etc.
Viability
Viability, in turn, considers whether we can build a business around the idea. Think: product-market fit. We could generate the following assumptions:<br>We believe...