Interview scorecard template

Network Performance Engineer interview scorecard

Evaluate Network Performance Engineer candidates across 4 weighted areas: technical depth, work that shipped, diagnosis under uncertainty, and working across the org. Technical depth leads at 35%, so check depth on throughput and latency mechanics: TCP window scaling, buffer bloat, QoS policy maps, BGP and OSPF path selection, and reading packet captures. Use the rubric to compare role-specific evidence consistently.

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engineering applied sciencebgp routinglatency optimizationnetwork performancepacket capture
TL;DR
For technical depth, look for evidence the candidate explains congestion control and queueing behaviour precisely, and interprets a capture or NetFlow record to name the real bottleneck. For work that shipped, look for evidence the candidate cites named links, sites or services with before and after metrics, and describes the change window and rollback plan used. Apply the written 1–5 anchors to every answer, record the evidence behind each rating, and use the factor weights to reach a consistent overall assessment.
Complete evaluation framework

What to assess and how to score it

Review the evidence signals before interviewing. Then use the anchored descriptions—not instinct alone—to choose the score that best matches each answer.

01
Evaluation factor

Technical depth

35% weight

Check depth on throughput and latency mechanics: TCP window scaling, buffer bloat, QoS policy maps, BGP and OSPF path selection, and reading packet captures in Wireshark or tcpdump.

Evidence to listen for

  • Explains the physics or mechanism behind their work, not just the tooling
  • Names the standards, tolerances, and constraints they designed against
  • Can defend a design decision under follow-up questions
  • Distinguishes what they personally engineered from what the team delivered

Five-point scoring guide

1
Poor

Cannot explain the fundamentals of their own stated specialism.

2
Needs Improvement

Knows the vocabulary but not the underlying mechanism; struggles under follow-ups.

3
Satisfactory

Solid working knowledge for the role; depth thins out on edge cases.

4
Very Good

Strong command of the domain; explains trade-offs and defends decisions well.

5
Excellent

Explains congestion control and queueing behaviour precisely, and interprets a capture or NetFlow record to name the real bottleneck.

02
Evaluation factor

Work that shipped

30% weight

Ask for a specific optimisation they delivered: baseline versus post-change figures for jitter, packet loss, p95 latency, or link utilisation, plus how the change was rolled out.

Evidence to listen for

  • Names specific programmes, parts, or systems that reached production or field use
  • States their own scope inside the project
  • Can give measured outcomes: yield, cycle time, cost, failure rate
  • Explains what went wrong and what they changed

Five-point scoring guide

1
Poor

No delivered work; experience is coursework, lab-only, or purely observational.

2
Needs Improvement

Contributed to projects but cannot say what shipped or what their part was.

3
Satisfactory

Has delivered real work; outcomes described without numbers.

4
Very Good

Names shipped work and their scope, with some measured results.

5
Excellent

Cites named links, sites or services with before and after metrics, and describes the change window and rollback plan used.

03
Evaluation factor

Diagnosis under uncertainty

20% weight

Probe an intermittent degradation they chased: how they isolated MTU issues, asymmetric routing, duplex mismatch or upstream ISP faults using iPerf, ThousandEyes or SNMP polling.

Evidence to listen for

  • Describes a real failure they chased to root cause
  • Shows a method: isolate variables, reproduce, measure, eliminate
  • Distinguishes correlation from cause
  • Says what they ruled out and why, not only what the answer turned out to be

Five-point scoring guide

1
Poor

No diagnostic method; guesses or escalates immediately.

2
Needs Improvement

Trial and error with no structure; cannot explain how they narrowed the cause.

3
Satisfactory

Reasonable method on familiar problems; less structured on novel ones.

4
Very Good

Clear systematic approach with a real root-cause story.

5
Excellent

Walks a layered elimination path, states what evidence ruled each hypothesis out, and admits which theories proved wrong.

04
Evaluation factor

Working across the org

15% weight

Assess how they work with NOC, security and application teams: escalations, capacity forecasts feeding budget, and defending a finding against a vendor blaming the network.

Evidence to listen for

  • Explains technical constraints to non-technical stakeholders without condescension
  • Has negotiated scope, cost, or timeline with manufacturing, product, or suppliers
  • Documents decisions so others can act on them
  • Takes review feedback without defensiveness

Five-point scoring guide

1
Poor

Cannot communicate outside their specialism; dismissive of other functions.

2
Needs Improvement

Communication gaps cause rework; avoids stakeholder contact.

3
Satisfactory

Works adequately with other teams; documentation is thin.

4
Very Good

Communicates clearly across functions; reliable collaborator.

5
Excellent

Describes translating packet-level evidence into service impact for application owners, and holding a carrier accountable with data.

Evidence-led prompts

Interview questions for a Network Performance Engineer

Use these prompts to surface evidence for the weighted factors above and compare candidates against the same role-specific criteria.

  1. 01

    What does your professional experience in network management involve?

  2. 02

    What is the largest network you have been responsible for, and what did you do?

  3. 03

    Can you describe your experience with network design and implementation?

  4. 04

    How do you typically diagnose network connectivity problems?

  5. 05

    How would you handle users reporting slowness when you find no fault?

See the complete Network Performance Engineer question set
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