Most senior engineering interviews still include some version of the same round: reverse a linked list, find the shortest path, solve a graph problem, forty-five minutes, on a shared screen, with someone watching. It's treated as neutral, almost scientific — a clean, objective signal in an otherwise fuzzy process. It measures something real. It just isn't the thing a senior engineer's job actually consists of.
This is aimed specifically at that format: the timed algorithm puzzle, solved alone from memory. Realistic debugging exercises, refactoring a real codebase, or reviewing an actual pull request together are a different thing, and much of what follows doesn't apply to them.
What a coding test actually measures
Strip away the language about "problem-solving," and a timed coding round measures a narrow, specific skill: pattern recognition under time pressure, on a puzzle engineered to have exactly one clever trick, with no reference material and no one to ask. That's closer to a timed academic exam than a workday. It rewards whoever has recently drilled the pattern being tested — which is a study habit, not an engineering competency, and one that decays within months of someone leaving an active interview cycle.
None of that makes the exercise meaningless. It's a real, measurable signal of something. The question is whether that something is the job you're hiring for.
What a senior or principal engineer's job actually is
In more than 25 years of building software, the hardest decisions I've watched senior engineers make were rarely about remembering an algorithm. They were about understanding a system nobody fully understood anymore, finding the least dangerous path forward, and explaining the tradeoff clearly enough that a team could actually act on it.
The job is mostly not writing code quickly from memory under a clock. Most of it is reading and understanding a large, already-existing system before touching it, then weighing a build-vs-buy or architecture decision whose consequences play out over quarters, not minutes. Code needs to be written so the next person, often a less experienced one, can read, trust, and safely modify it eight months later. Someone has to notice the failure mode nobody thought to ask about. Often the highest-leverage move is recognizing that the right answer isn't more code at all.
The real version of a senior engineer's "test" looks like a design doc, a pull request review, an incident postmortem, a migration plan. All of it done with time to think, with the actual system in front of them, with the ability to search, ask a colleague, and revise before anything ships.
A coding test rewards whoever has spent the last month grinding practice problems. It tells you very little about whether they've shipped and sustained a system that stayed reliable for years, which is a considerably harder thing to be good at, and the thing you're actually paying a senior salary for.
The mismatch: testing the opposite of how code actually gets written
Lay the two side by side and, for a traditional algorithmic coding round, the mismatch can be substantial. Real engineering code gets written slowly and deliberately, with documentation open, with a colleague to ask, over hours or days, in a system with real history and real constraints, revised through code review before it ships. A coding test asks someone to produce correct code from memory, alone, against a clock, on a problem built specifically to have no context behind it. That's not a rough approximation of the job for most senior work — it's close to the reverse of the conditions under which that work actually gets done.
Coding tests are a legitimate tool — for a different job
None of this means the coding test is a bad interview format. For junior hiring, a scoped coding exercise can measure genuinely useful fundamentals: whether someone can translate a clear requirement into working code, reason through basic data structures, communicate their approach, and recover when they get stuck. Those skills make up a large share of what an early-career engineer is initially hired to demonstrate, even though they shouldn't be the only thing a junior process evaluates — plenty of junior roles also involve real collaboration, unclear requirements, and debugging systems nobody handed them a clean spec for.
Put plainly: a coding test can be a useful tool when hiring for a role centered on executing clearly defined implementation work. There's real value in engineers who can take a well-scoped requirement and deliver reliable code efficiently. But for a senior or principal role, execution is only part of the job. You're also hiring someone to clarify ambiguous problems, evaluate tradeoffs, reduce risk, and shape the work before implementation even begins. A test engineered to reward fast recall on a fake problem is the wrong instrument for finding that person, no matter how much harder you make the puzzle.
Coding tests remain popular for understandable reasons: they're repeatable, easy to schedule, and look more objective than an unstructured conversation. The problem isn't standardization itself, it's standardizing the wrong signal. A senior-level process can and should still use a consistent rubric — that rubric just needs to score architectural judgment, risk identification, communication, and tradeoff reasoning, instead of recall speed on an invented puzzle.
What to test instead, for senior and principal roles
A few formats actually exercise the skill you're hiring for:
- Review a real piece of code or architecture. Hand them something real (anonymized, if needed) from your own system and have them walk through it — what's right about it, what they'd change, what they'd want to know before touching it. This tests judgment against a real artifact instead of recall against an invented one.
- Walk through a real past decision. Have them narrate an actual technical call they made: the context, the alternatives they weighed, what they'd do differently now. It's difficult to fake convincingly once an interviewer asks detailed follow-up questions about the constraints, the alternatives, and the actual outcome, and it directly reveals how someone thinks under ambiguity.
- A short, paid work-sample exercise — based on a fictional or previously-solved problem, never live production work, with a fixed time limit and normal working conditions: documentation, search, even AI assistance, all allowed. This mirrors the actual job instead of a deliberately stripped-down version of it, without asking anyone to do free labor.
- A system design discussion on a problem shaped like your actual problem, not an abstract "design Twitter" exercise. It evaluates planning and tradeoff reasoning instead of memorized reference architectures.
- Reference conversations that ask about judgment, not just delivery. How did they operate under ambiguity, how did they handle disagreement, did their designs hold up a year later. This is where "did it run three years later" actually gets checked.
Where this leaves you
The coding test isn't worthless. Traditional algorithm puzzles are simply aimed at the wrong signal for many of the senior roles where they're still used. Keep them, or something like them, for early-career hiring and roles centered on narrowly scoped implementation work.
When you're hiring judgment, build a process that actually exercises judgment: a real artifact, a real past decision, and a problem shaped like the work the candidate will actually perform, with the time and context the job itself would provide. Otherwise, the process mostly tells you who's prepared for the interview format, not who will exercise the best judgment once hired.
If your hiring process is still screening senior candidates the same way it screens junior ones, tell us what the role actually needs and we can help you design an evaluation that measures it.