Q: Your AWS bill doubled this month unexpectedly. How do you investigate?
1. AWS Cost Explorer — open it, filter by service. Which service increased?
#AWS #Cost & Architecture #L3 #Cloud #Infrastructure #EC2
🎙️ Candidate Opening & Architectural Context
""In our AWS cloud environment, we managed high-traffic microservices where this exact scenario occurred. When addressing this question, I walk the interviewer through our production incident runbook: isolating the blast radius, checking diagnostic logs and metrics, and applying a safe fix.""
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🛠️ Production Runbook & Step-by-Step Resolution
1️⃣
Initial Diagnostics & Root Cause Analysis
- AWS Cost Explorer — open it, filter by service. Which service increased?
- Filter by time — compare this month vs last month. Find the day the cost jumped.
- Cost and Usage Report (CUR) — most granular billing data. Query with Athena if needed.
- Check for data transfer — inter-region, internet egress. A new service sending data outside AWS is expensive.
- Check EC2 instances — a runaway Auto Scaling group could have spawned many instances.
2️⃣
Remediation & Permanent Safeguards
Execute the resolution runbook and verify workload health:
- Check NAT Gateway — NAT Gateway charges per GB. A bug causing high-volume traffic through NAT is a common culprit.
- Check CloudWatch — too many custom metrics or log ingestion.
- Enable AWS Budgets — set alerts to catch this earlier next time.
- Enable Cost Anomaly Detection — ML-based alerts for unusual spend patterns.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: AWS Cost Explorer — open it, filter by service. Which service increased?."
⚡ 60-Second Elevator Pitch Talking Points
- AWS Cost Explorer — open it, filter by service. Which service increased?
- Filter by time — compare this month vs last month. Find the day the cost jumped.
- Cost and Usage Report (CUR) — most granular billing data. Query with Athena if needed.
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