How would you troubleshoot high latency from an EC2 instance?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of AWS conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
Work from the outside in and use metrics before guessing.
- Confirm scope: is it the instance, the network, the application, or a dependency? Check CloudWatch CPU, network, and EBS metrics and the ALB target response time.
- Network: use VPC Flow Logs, check for packet loss, and test with ping, traceroute, or curl timing from a bastion.
- Instance: SSH in and run top, vmstat, iostat, and sar to see CPU steal, memory pressure, and disk I/O.
- EBS: burst-credit exhaustion on gp2 or throttled IOPS on gp3 shows as high await.
- Application: enable tracing, and inspect slow queries, thread pools, and GC pauses.
sudo iostat -x 1 5
sudo ss -s
curl -o /dev/null -s -w '%{time_total}\n' https://example.com
Right-size the instance, move to gp3, or fix the query. Check whether the bottleneck is a downstream dependency.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.