Q: Design a highly available, scalable web application architecture on AWS for a startup that expects unpredictable traffic.
Production scenario covering Design a highly available, scalable web application architecture on AW.
#AWS #Cost & Architecture #L3 #Cloud #Infrastructure #ALB
🎙️ Candidate Opening & Architectural Context
""In a previous role, our monitoring paged me for a similar incident across our AWS VPC infrastructure. 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
Key design decisions:
- Fargate — no instance management, auto-scales, pay per task (good for unpredictable traffic).
- Multi-AZ everything — ALB, RDS, ECS tasks across at least 2 AZs.
- CloudFront — reduce load on origin for static content.
2️⃣
Remediation & Permanent Safeguards
Route 53 (DNS + health checks)
↓
CloudFront (CDN for static assets + caching)
↓
ALB (Application Load Balancer, multi-AZ)
↓
ECS Fargate (auto-scaling container tasks, multi-AZ)
↓
RDS (Multi-AZ, with read replicas)
RDS Proxy (connection pooling)
ElastiCache Redis (session store + caching)
↓
S3 (static assets, uploads)- Route 53 health checks — failover to secondary region if primary is down.
- Auto Scaling on ECS — scale based on CPU/request count with target tracking.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: Fargate — no instance management, auto-scales, pay per task (good for unpredictable traffic).."
⚡ 60-Second Elevator Pitch Talking Points
- Fargate — no instance management, auto-scales, pay per task (good for unpredictable traffic).
- Multi-AZ everything — ALB, RDS, ECS tasks across at least 2 AZs.
- CloudFront — reduce load on origin for static content.
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