Q: Your monitoring dashboard shows that a server's memory usage has been steadily climbing 1% per day for two weeks. The application developers say "it's fine." How do you approach this as an SRE?
A steady, linear increase in memory usage is a classic memory leak pattern. Even if the application functions today, at 1%/day, the serve...
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🎙️ Candidate Opening & Architectural Context
""Never reboot a server blindly; always capture top process telemetry, lsof descriptors, and thread dumps first. The interviewer is testing: Capacity planning, trend analysis, proactive SRE.. I structure my answer around systematic triage first, root cause analysis second, and permanent remediation third.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
A steady, linear increase in memory usage is a classic memory leak pattern. Even if the application functions today, at 1%/day, the server will OOM in approximately 2–3 weeks.
- Quantify the risk:
- Current usage: 70% → OOM in ~30 days
- Calculate the exact date the server will hit critical threshold (e.g., 95%)
- Present a clear timeline to developers: "This server will crash on [date] without intervention"
- Gather evidence:
- Identify the leaking process: Compare RSS (Resident Set Size) growth across processes. The one growing linearly is the culprit.
2️⃣
Remediation & Permanent Safeguards
SRE approach: Never dismiss a linear trend—it's a countdown timer to an outage.
# Track per-process memory growth
ps aux --sort=-%mem | head -20
# Check for growing heap
pmap -x <PID> | tail -1
# Monitor over time
pidstat -r -p <PID> 60
- Short-term mitigation:
- Schedule periodic application restarts during off-peak hours
- Set up memory-based alerts at 85% and 95%
- Implement cgroup memory limits to prevent one process from OOMing the entire server
- Long-term fix: Work with developers to profile the application using language-specific tools (Valgrind for C/C++, heap dumps for Java, memory profilers for Python/Go).
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Quantify the risk:."
⚡ 60-Second Elevator Pitch Talking Points
- Quantify the risk:
- Current usage: 70% → OOM in ~30 days
- Calculate the exact date the server will hit critical threshold (e.g., 95%)
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