Why pre-screen network performance engineers before the technical interview
The hard tickets are the ones where every graph is green and users say it is slow. The cause is usually somewhere the monitoring does not reach: a duplex mismatch, an application waiting on a name lookup, a path that changed last week. Engineers worth hiring have a method for that. A short screen asks how they proceed when the obvious checks come back clean.
What actually matters when screening Network Performance Engineer candidates
- 01
Technical depth
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.
- 02
Work that shipped
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.
- 03
Diagnosis under uncertainty
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.
- 04
Working across the org
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.
Pre-screening questions to ask Network Performance 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.
Networks they ran
3 questions01What does your professional experience in network management involve?
Listen forScale, sites and technologies described, with what they were personally responsible for made clear.
Experience described without scale, or responsibility limited to raising tickets with vendors.
02What is the largest network you have been responsible for, and what did you do?
Listen forUser and site counts with their duties, and the operational reality of running it described.
Scale overstated, or duties described in terms nobody could verify.
03Can you describe your experience with network design and implementation?
Listen forDesigns they produced and delivered, with resilience and growth planned into the topology.
Design work limited to following a vendor reference, or resilience added after an outage.
Diagnoses the invisible
3 questions04How do you typically diagnose network connectivity problems?
Listen forA layered method from physical upward, with each assumption tested rather than assumed.
Diagnosis by restarting equipment, or changes made before the cause is understood.
05How would you handle users reporting slowness when you find no fault?
Listen forCaptures taken from the user's position, with application behaviour and name resolution examined.
The report dismissed as perception, or investigation stopping at interface statistics.
06Can you describe the most challenging performance problem you solved?
Listen forA genuinely obscure cause found by evidence, with the reasoning described step by step.
Problems resolved by replacing hardware, or causes never confirmed after the symptom stopped.
Routing depth
4 questions07How familiar are you with routing, including dynamic routing protocols?
Listen forProtocol behaviour understood including convergence and path selection, learned from real troubleshooting.
Routing knowledge limited to static configuration, or convergence behaviour never observed.
08Can you describe your experience with local and wide area infrastructure?
Listen forBoth understood with the different failure modes and performance characteristics of each.
Wide area links treated like local ones, or latency and loss effects not understood.
09Are you experienced in managing wireless networks?
Listen forCoverage, interference and client behaviour understood, with surveys used rather than guesswork.
Wireless problems solved by adding access points, or interference never measured.
10How familiar are you with network security controls and protocols?
Listen forSegmentation and access control implemented in practice, with rules reviewed rather than accumulated.
Firewall rules only added and never removed, or security treated as another team's concern.
Explains it clearly
2 questions11Do you have experience with scripting for network tasks?
Listen forRepetitive configuration and checks automated, with changes applied consistently across all devices.
All configuration done device by device, or no way to audit what is actually deployed.
12Tell me about explaining technical information to a non-technical audience.
Listen forA plain explanation that keeps the cause intact, with impact described in terms users care about.
Explanations full of terminology, or users told the problem was too complex to explain.
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 depth
35%5Explains congestion control and queueing behaviour precisely, and interprets a capture or NetFlow record to name the real bottleneck.
Work that shipped
30%5Cites named links, sites or services with before and after metrics, and describes the change window and rollback plan used.
Diagnosis under uncertainty
20%5Walks a layered elimination path, states what evidence ruled each hypothesis out, and admits which theories proved wrong.
Working across the org
15%5Describes translating packet-level evidence into service impact for application owners, and holding a carrier accountable with data.
Every graph is green and users say it is slow. A one-way video screen asks what they do next.
Try it on HirevireScreening FAQ
Process basics
How long should a pre-screening round for this role take?
Fifteen minutes across eight to ten questions, answered async. Enough to establish networks they ran, test their diagnostic method, and check routing and infrastructure depth.
How much automation should I expect?
Enough to script repetitive checks and configuration. An engineer configuring every device by hand will make inconsistent changes and struggle to audit what is deployed.
Evaluating answers
What is the strongest signal when screening this role?
How they proceed when everything looks fine. Strong engineers work up the layers with packet captures and timing. Anyone who escalates to the provider immediately adds little to the process.
How do I judge their depth?
Ask them to explain a fault to a non-technical audience. Real depth shows in a plain explanation with the cause intact. Vagueness usually means the fault was never understood.
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
