Updated September 2026
Interview a startup senior backend engineer in four stages: a screen on motivation and scope, a deep dive on a system they ran in production, a design session on a real problem from your roadmap with a take-home debrief, and a final conversation with the team. The theme running through all four is ownership, meaning whether they have built, shipped and run systems themselves.
The senior backend interview plan
Production ownership
- Pick a service you ran in production. Draw it for me and tell me where it was weakest.
- Tell me about the worst outage you were involved in. What did you do, minute by minute?
- What alerts did you get rid of, and why?
- How do you run a database migration on a large table without downtime?
- Tell me about a bug that took you more than a day to find.
Strong answer: first-hand detail, including what they got wrong, and fixes that changed the system rather than just the symptom.
Red flags: describes a team's work as "we" throughout and can't say what they did, or has never been on call.
Data and API design
- Here is a feature from our roadmap. How would you model the data?
- When would you choose not to use a relational database?
- How do you design an API that other teams will call for years?
- How do you make a job safe to run twice?
- Tell me about a data model you designed that later caused pain. What would you change?
- How do you decide when to split something into a separate service?
Strong answer: asks about access patterns and volume before choosing a design, and talks about idempotency and versioning without prompting.
Red flags: reaches for microservices or a new database by default, or can't explain how their design handles failure.
Working from a rough brief
- A founder asks for "better reporting" for customers. What do you ask before you write any code?
- Tell me about a time you shipped a smaller version of what was asked for. How did it go?
- What do you do when you disagree with the product decision behind a ticket?
- How do you estimate work you've never done before?
- What does a useful design doc look like to you?
Strong answer: questions about the user and the problem first, a small first version, and disagreement raised early with a proposal.
Red flags: needs a full spec to start, or quietly builds something different from what was agreed.
Startup fit
- What is the smallest engineering team you have worked in? What was hard about it?
- How do you feel about being on call, and what makes a rota fair?
- Which part of our backend would you want to own first, from what you've seen?
- What would make you leave a startup within a year?
Strong answer: comfortable with breadth, reasonable expectations about on-call, and curiosity about your system specifically.
Red flags: expects a platform team to handle operations, or shows no interest in your product.
Work sample: a small service from an unclear brief
Ask for a small service that receives webhook events from a payment provider, stores them, and exposes a summary endpoint per customer. Leave some things unspecified on purpose: duplicate events, events arriving out of order, and how much history to keep. Cap it at three hours and ask for a short README explaining decisions and what they would do next.
Look for idempotent handling of duplicates, sensible data modelling, tests on the risky parts, and a README that names trade-offs. In the debrief, ask what they left out and why. That tells you more than the code.
Scoring rubric
| Outcome | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Service ownership | Never ran a service | Ran one with support | Owned a service and its incidents | Made a fragile service dependable |
| Data and API design | Design ignores access patterns | Works, but hard to change | Clear model, versioned APIs | Anticipates change without over-building |
| Reliability | Not considered | Fixes symptoms | Fixes causes, writes postmortems | Improved alerting and on-call for a team |
| Delivery | Take-home unfinished, no notes | Finished, few trade-offs noted | Small, working, clear README | Shipped the right slice and explained it well |
| Raising the bar | No examples | Reviews others occasionally | Writes docs and reviews others use | Changed how the team works |
Where Funded.club fits
A dedicated Funded.club recruiter screens backend candidates for production ownership before you spend time on interviews. You see first screened candidates within 7 days, on a fixed fee agreed upfront (see pricing).
Frequently asked questions
Should senior backend engineers do a take-home test?
A short one, yes, if it is capped at three hours and you debrief it with them. Many senior candidates prefer a take-home to live coding, and it shows how they work from an unclear brief.
How do I interview a backend engineer if I'm not technical?
Run the screen and the startup fit questions yourself, and bring in a senior engineer or adviser for the deep dive and design stages. Use the scorecard in our senior backend engineer job description template so everyone scores the same things.
Is a senior backend engineer the same as a founding engineer?
At Seed they can overlap. A founding engineer usually carries more product scope and equity. Our guide to hiring a founding engineer covers the differences.
Worth a brief chat about your next hire? Book a free call.
Hiring after a funding round?
First candidates in 7 days. Fixed-fee, no commission.