What to assess in a senior software engineer
A senior engineer multiplies a team. Assess the decisions they make and how they explain them, not only the code they write.
- System design: choosing components, defining boundaries, and naming what will break first.
- Trade-offs: cost, speed, reliability and simplicity, and saying which one they are giving up.
- Codebase judgement: reading unfamiliar code and knowing where a change belongs.
- Directing AI: planning a change, briefing the assistant, and reviewing its output like a pull request.
- Leadership: mentoring, unblocking others, and raising risks early.
- Incident experience: what they did, what they learned and what they changed.
System design questions on the whiteboard
Design sections open a whiteboard beside the conversation. The board is saved with each answer and described to the screener, so its follow-ups are about the candidate's own diagram. Other languages and stacks are covered in conversation; hands-on code in the screen is TypeScript on Node.
- Draw a notification system that sends email, push and in-app messages. Where do duplicates come from?
- Your service's p99 latency doubled after a deploy with no obvious change. Walk me through the next hour.
- How would you split a monolith's billing code into its own service, and would you?
- Describe a design decision you made that turned out wrong. What did it cost and what did you do?
- How do you review a large change an AI agent made across many files?
The coding round and the hiring manager round
For senior candidates, the coding round's Plan, Build and Review flow is revealing. They can write a plan document the assistant is briefed on, build with completions, chat and an agent, and review their change as a diff against the starting files. Run it unguarded to see how they direct a full assistant.
The hiring manager round sits on the same record. A meeting notetaker can join to capture audio and a transcript (2 credits per started hour), or you can upload a recording. The interviewer writes the round up, and the write-up joins the one scorecard.
AI-fluency signals at senior level
| Signal | What it tells you about a senior engineer |
|---|---|
| Time to first prompt | Whether they planned the change before handing work to the assistant. |
| Prompt quality | Whether briefs read like a good ticket: context, constraints, acceptance criteria. |
| AI-generated share | How much was delegated. At senior level, high delegation with strong verification can be a good sign. |
| Verification | Whether delegated work was tested and reviewed before moving on. |
| Over-reliance flags | Large agent changes accepted without review. |
| Recovery | How quickly they redirected the assistant when it went the wrong way. |
From evidence to a decision
The screen, the coding round, the hiring manager round and any bar raiser sit on one scorecard. The lowest verdict sits next to the average, so a mean of 4.1 cannot talk you past a strong no. A named person records the outcome.
Questions
Can an AI screen assess system design?
It can gather structured evidence. The screener asks design questions from your plan, reads the candidate's whiteboard, and follows up. Each score cites the answers, and a person decides.
Is a coding round useful for senior engineers?
Yes, when it shows judgement. The Plan, Build and Review flow and an unguarded assistant show how they direct and check work, which is much of a senior engineer's day.
Can I record the hiring manager interview?
Yes. A meeting notetaker can capture audio and a transcript, or you can upload a recording. Video is not captured.
How do I avoid a high average hiding a strong no?
SynergicHire's scorecard shows the lowest verdict next to the average for every candidate.