Why pre-screen full stack engineers before the technical interview
The label covers a wide range, from engineers genuinely comfortable at both ends to people who write backend code and can follow a component library. Both are useful and they are not the same hire. What is rarely honest on a resume is the imbalance. A short screen establishes where the depth is, and it surfaces the one thing that predicts a lot in either half: what they did the last time something broke in production.
What actually matters when screening Full Stack Engineer candidates
- 01
Technical proficiency
Check depth on both ends: React or Vue state handling, Node or Django API layers, SQL schema design, migrations, and how they handle auth flows like OAuth or JWT.
- 02
Systems and trade-offs
Probe architecture calls they owned: REST versus GraphQL, monolith versus service split, caching with Redis, background jobs, and what they knowingly deferred as technical debt.
- 03
Evidence and rigour
Test how they prove code works: test pyramid coverage, Playwright or Jest suites, CI gates, error budgets, and how they debugged a production incident from logs or traces.
- 04
Collaboration and communication
Assess how they work with designers, product managers, and reviewers: pull request review habits, ticket scoping, handling Figma handoffs, and unblocking others during sprints.
Pre-screening questions to ask Full Stack Engineer candidates
12 questions grouped by what they test. Ask the same set in every screen and score answers on a consistent scale, or send them as an async video screen and compare answers side by side.
Built across both ends
3 questions01Can you explain a complex project you worked on and how you managed the full stack?
Listen forA system where they owned both ends, with a decision at one end driven by a constraint at the other.
A project where someone else owned half, or no decision that crossed the boundary.
02Can you give an example of how you built a scalable system and the technologies you used?
Listen forScale described with actual numbers, with the bottleneck they hit and what they did about it.
Scalability claimed with no load figures, or architecture chosen for volumes that never arrived.
03Can you explain your experience with both front-end and back-end development?
Listen forAn honest statement of which end they are stronger at and how they compensate on the other.
Equal senior depth claimed at both ends, or an imbalance the rest of the answers contradict.
Where the gap is
4 questions04Which backend programming language do you work in most?
Listen forReal depth in one language including its concurrency and memory behaviour, tied to systems they built.
Language knowledge that stops at framework usage, or several claimed at equal depth.
05Which frontend frameworks do you have experience in?
Listen forEnough depth to reason about state and rendering, not just assemble components from a library.
Frontend work limited to following patterns, or no understanding of what the framework does underneath.
06What is your experience with databases, and which types have you worked with?
Listen forQuery plans read and schemas designed, with a migration run against a live table.
Database work limited to what an ORM generates, or no experience changing a schema under traffic.
07What experience do you have with API development and integration?
Listen forContracts designed with versioning considered, and error and loading states handled on the consuming side.
Breaking changes shipped without a migration path, or only successful responses handled.
Testing and delivery
2 questions08How do you approach testing in full stack development?
Listen forA view on what is worth testing at each level, with a bug their tests caught before release.
Testing described as the quality team's responsibility, or tests written to hit a coverage number.
09What is your experience with delivery practices and continuous integration?
Listen forPipelines they worked with daily, including how quickly a broken build gets fixed and who fixes it.
A pipeline routinely left red, or deployment described as another team's responsibility entirely.
Production incidents
3 questions10Can you describe a time when you optimised a web application for better performance?
Listen forA problem found by measurement with the metric before and after, and what the fix cost elsewhere.
Optimisation applied without profiling, or performance work with no numbers attached.
11Can you explain a situation where you had to troubleshoot a production issue?
Listen forA live incident with what they checked, what they ruled out and what changed afterwards.
No production incident they can describe, or a problem resolved with the cause never established.
12What is your approach to handling security issues in a web application?
Listen forCommon classes of vulnerability understood in practice, with a real issue they found and fixed.
Security described as a checklist, or authentication and authorisation treated as the same thing.
How to score responses
Score every candidate on the same four criteria immediately after the screen. At this stage you are shortlisting for panel interviews, not making the final call.
Technical proficiency
35%5Names frameworks and versions precisely, explains query optimisation or component re-render fixes, and shows comfort from database index to browser paint.
Systems and trade-offs
25%5Walks through a specific trade-off with load numbers, cost, and team size, plus the failure mode they accepted and later revisited.
Evidence and rigour
25%5Cites concrete evidence such as p95 latency before and after, Sentry error rates, or a failing test that caught a regression pre-release.
Collaboration and communication
15%5Describes review comments that changed a design, negotiates scope with product owners, and writes docs or runbooks colleagues actually use.
The label covers everything from genuine breadth to a backend engineer who can follow a component library. A one-way video screen finds the imbalance.
Try it on HirevireScreening FAQ
Process basics
How long should a pre-screening round for a full stack engineer take?
Fifteen minutes across eight to ten questions, answered async. Enough to establish where their depth actually is, hear one production incident, and check their testing and delivery habits.
Should I expect equal depth at both ends?
No, and a candidate claiming it is usually overstating. Ask which end they are stronger at and check that the weaker half is adequate for what you need rather than absent.
Evaluating answers
What is the strongest signal when screening this role?
Admitting which end they are weaker at. Honest engineers say so immediately and describe how they compensate. Anyone claiming equal senior depth across the whole stack is usually thin somewhere.
How do I judge their production experience?
Ask about an incident they debugged live. Real answers describe what they checked, what they ruled out and what they changed afterwards. Anyone with no production incident has not carried a system.
Go deeper on this role
Sanat has been hiring since 2012 and watching the recruitment industry change up close ever since, and turned that screening process into Hirevire's video screening platform. LinkedIn
