Short version: if you cannot read code, stop trying to evaluate code. You will fail at it and the candidate will know within five minutes. What you can evaluate, better than most technical interviewers do, is judgment, communication, and how someone behaves under uncertainty. Those are the things that decide whether a senior engineer is worth the offer. Borrow a technical read for the parts you genuinely cannot do, and own the parts you can.
I get pulled into a lot of first-engineer interviews where the founder is brilliant about the business and visibly anxious about the technical screen. They have read that they should ask about data structures, they have a list of terms they do not understand, and they are about to spend an hour pretending to understand answers they cannot evaluate. That interview filters for nothing. Here is the one I run instead.
You are not judging code. You are judging judgment.
A senior engineer's value is not that they can write a function. Plenty of cheaper, more junior people can write a function, and so increasingly can the tools. What you are paying a senior engineer for is the judgment to choose what to build, what to skip, what will break in six months, and when to tell you that the thing you asked for is a bad idea. That judgment is exactly what a non-technical founder is well equipped to assess, because it shows up in plain language, not in syntax.
So reframe the whole interview. You are not checking whether they can code. Assume competence is real and verify it cheaply elsewhere. You are checking whether they can reason about trade-offs, explain a hard decision to someone without their background, and stay honest when they do not know something. I have watched founders pass on a strong candidate because they could not follow the technical answer, and hire a weak one because he sounded confident. Confidence is the easiest thing to fake and the most expensive thing to mishire on. This is the same bet I described in your first senior engineer is a bet, and the interview is where you set the odds.
The questions that reveal judgment
Good questions are open, specific to real situations, and impossible to answer with a memorized definition. These are the ones I lean on.
Walk me through a technical decision you regret. The answer tells you whether they reflect, whether they can admit a mistake, and whether they understand why it was wrong rather than just that it was. A senior engineer has regrets and can name them. Someone who claims they have none is either junior or not honest.
Tell me about a time you pushed back on a founder or a product manager. You want to hire someone who will tell you no when you are wrong, and this question shows whether they can disagree without being difficult. If every story is about heroically delivering whatever they were told, that is a yes-machine, and a yes-machine is dangerous as your first engineer.
Here is something we are considering building. How would you approach it, and what would you want to know before starting? Use a real problem from your roadmap. You are listening for the questions they ask, not the answer they give. A strong engineer interrogates the problem before solving it. A weak one starts naming technologies immediately.
What is the simplest version of this that would teach us something? This separates the engineers who want to build the impressive thing from the ones who understand that an early-stage company is buying speed and learning, not architecture. The second kind is who you want.
Borrow the technical read you don't have
There is one part you cannot do, and you should not pretend otherwise: confirming that the person can actually build at the level they claim. Borrow that read. Bring in a technical advisor, a fractional CTO, or a trusted senior engineer from your network for one focused conversation with each finalist. Their job is narrow. Confirm depth, probe the technical stories for substance, and sniff out exaggeration. Your job is everything else.
Split the work explicitly. You assess communication, motivation, honesty, and product sense, the things you read well. Your technical helper assesses whether the engineering is real. Do not blur the two. The failure I see most is a founder trying to be the technical judge, getting it wrong, and either hiring on charisma or rejecting on vocabulary. If you do not have someone to borrow this read from, that gap is itself a reason to get outside help before you hire, which is part of what a codebase and hiring teardown is for.
Take-home over whiteboard, with limits
For senior candidates, a small take-home that mirrors a real problem from your product tells you far more than a whiteboard puzzle. You see how they actually work, how they communicate decisions, what they choose to skip, and how they use modern tools to move faster. Whiteboard algorithm trivia has become close to useless for early-stage hiring, where ambiguity and product intuition matter more than reciting textbook solutions.
Two rules keep the take-home fair. Keep it short, a few hours at most, and pay for the candidate's time if it runs longer, because senior people have options and resent unpaid spec work. And review it with your technical helper, walking through the choices with the candidate rather than grading silently, because the explanation of the decisions tells you more than the code itself. What you are really measuring is the judgment underneath, which is most of what senior engineering judgment is worth paying for.
A timeline that respects everyone
Senior engineers move fast and have other offers, so a slow, vague process loses the best people. Aim for two to three weeks end to end. Week one, screening calls and the take-home. Week two, the deeper conversations, including the borrowed technical read. Week three, references and an offer. Tell candidates the shape up front. The ones worth hiring respect a founder who runs a tight, honest process, and they read a sloppy one as a preview of what working for you will feel like.
Frequently asked questions
How can I tell if a senior engineer is technically strong if I can't code?
You mostly cannot, directly, and you should not try to fake it. Borrow that specific read from a technical advisor or fractional CTO for one focused conversation per finalist, and spend your own time on the things you assess well: judgment, honesty, communication, and product sense. Those decide most mishires, and you read them better than you think.
Should I give a senior engineer a coding test?
A short, realistic take-home tied to your actual product beats a whiteboard puzzle for senior candidates. Keep it to a few hours, pay for longer ones, and review it as a conversation about the decisions rather than a silent grade. The reasoning behind the choices is the signal, not whether the code compiles.
What interview questions reveal engineering judgment?
Ask for a technical decision they regret, a time they pushed back on a founder, how they would approach a real problem from your roadmap, and what the simplest useful version would be. These resist memorized answers and surface how someone reasons about trade-offs, admits mistakes, and resists over-building.
Do I need a technical person in the room to hire my first engineer?
For the verification of real technical depth, yes, you should borrow that read once per finalist. For everything else, you are the right judge. If you have nobody to borrow it from, treat that as a signal to get outside technical help before you make the hire, not a reason to wing it.