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Reference check questions for software engineers

Questions for the engineering managers, tech leads and peers who reviewed a developer’s code and shared their on-call rotation, grouped by what a team relies on.

By Never Ending SolutionsPublished October 8, 20265 min read

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Key takeaways

Use references for what a coding exercise cannot show: how the candidate’s code held up, how they took review and what they did when production broke.
Ask a peer who reviewed the candidate’s code often, not only the manager who saw their work in planning meetings.
Ask which parts of a system the candidate built themselves, so a team’s achievement is not credited to one person.
For a senior role, ask someone the candidate mentored how they explained decisions and reviewed other people’s work.

A technical interview shows how a candidate solves a problem in an hour with a stranger watching. The job is months of changing code other people wrote, reviewing and being reviewed, and fixing things at inconvenient times. The people who worked in the same codebase know how the candidate’s changes held up, how they responded when a reviewer pushed back and what they did when something they shipped broke.

Ask about specific systems and specific incidents. Engineering is collaborative, so separate what the candidate built from what the team built: when a reference says "we" throughout, ask which parts were the candidate’s.

Who to ask

An engineering manager or tech lead who assigned the candidate’s work and saw how their estimates compared with delivery.
A peer who reviewed their code often, ideally someone who also maintained code the candidate wrote.
A product manager or designer who planned around the candidate’s estimates and relied on their account of what was feasible.
For a senior role, an engineer they mentored, for how the candidate teaches, reviews and makes room for other people’s ideas.

Questions to ask, by competency

Choose the competencies that matter most for the position and two or three questions from each. Ask every reference the same set, and when an answer is a rating, ask for the example behind it.

Code quality and design

Code is read and changed far more often than it is written, so ask how the candidate’s work held up for the people who maintained it.

When you had to change code the candidate wrote, what was it like? Was it easy to follow, and were there tests you could trust?
Tell me about a design decision the candidate made on a system you both worked on. What trade-off did they choose, and how has it held up?
Where would you place the candidate’s code on a scale of 1 to 5 against the strongest engineer on that team, and what example puts it there? (rating)

Code review

Review is where engineers catch each other’s mistakes and teach each other. How a candidate gives and takes review affects the whole team.

How did the candidate respond when a reviewer asked for substantial changes to their work? Can you recall a specific change request?
What were the candidate’s own reviews like? Did they catch real problems, and how did the authors feel about the comments?

Incidents and on-call

Production fails eventually. The people who were there know whether the candidate stayed calm, kept others informed and owned their part.

Tell me about an outage or serious bug the candidate helped fix. What did they do first, and who did they keep informed?
When a problem traced back to the candidate’s own change, how did they handle the review afterward?
How dependable was the candidate during their on-call shifts, and how useful were their notes to the next person on the rotation?

Estimates and collaboration

Product managers, designers and other teams plan around what engineers say they can deliver, and when.

How accurate were the candidate’s estimates, and when work ran late, how early did they say so?
Describe a disagreement the candidate had with a product manager or another team about scope or approach. How was it settled?
How well did the candidate explain technical limits to people who were not engineers? Can you give an example?

Close the reference

End every reference the same way: ask whether they would hire or work with the candidate again and why, what support would help the candidate do their best work, and whether there is anything else you should know. The general question bank explains why the first of these matters most.

Checks a reference does not replace

Current skills, with a work sample. A reference describes how the candidate worked. A short exercise or a review of real code shows how they work now, so use both.
Public code the candidate points to. If they cite open-source work, read the review threads as well as the code: they show how the candidate gives and takes feedback in public.
Degrees or certifications the role requires, with the school or the body that issued them.

Warning signs to follow up

More than one reference calls the candidate "brilliant, but hard to work with".
The candidate described a system as their own, and references describe a team project in which the candidate built one part.
Incident stories in which the cause is always someone else’s code or another team’s mistake.
No reference worked in the same codebase: only managers at a distance or colleagues from other departments.
Estimates that slipped again and again, with the team finding out at the deadline.

One warning sign is a reason to ask another question, not a verdict. Reference check red flags covers how to check a concern fairly.

Send these questions to every reference

In ReferenceCheck, the candidate records consent and names their references from a secure link, each reference answers your questions on their phone, and you get one scored report. Candidates and references do not need accounts.

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Questions to leave out

Ask only about the work. Before an offer, the EEOC’s guidance says an employer may not ask a third party, such as a former employer, any question it could not ask the candidate directly. Leave out health, medical leave, age, family plans and other protected characteristics. What to leave out has the full list.

Common questions

Do you need references if a software engineer passed the technical interview?

Yes. The interview shows how the candidate solves a problem today, and references show how they worked with a team over months. The U.S. Office of Personnel Management notes that reference checks predict job performance, training success, promotion potential and turnover better than years of education or experience, though less well than cognitive ability tests.

Who should give a reference for a software engineer?

An engineering manager or tech lead, plus a peer who reviewed the candidate’s code. A manager sees delivery and a reviewer sees the code itself. For a senior engineer, add someone the candidate mentored.

What if a developer cannot list their current manager as a reference?

That is common when the candidate’s employer does not know they are looking. Ask for a former manager and a peer who has since left the company, and agree with the candidate whether to contact the current manager after a conditional offer.

Sources

U.S. Office of Personnel Management, Reference Checking. Checked October 8, 2026.
U.S. Equal Employment Opportunity Commission, Enforcement Guidance: Preemployment Disability-Related Questions and Medical Examinations. Checked October 8, 2026.

About this guide

Written and kept up to date by Never Ending Solutions, the company that builds NES ReferenceCheck. Outside facts are cited with the date we checked them, and the advice works with or without our software. Read our editorial standards.