Q: What is the difference between an Application Load Balancer (ALB) and a Network Load Balancer (NLB)? When do you use which?
- ALB (Layer 7): Operates at the Application layer. It understands HTTP/HTTPS headers, URLs, and cookies. You use it when you need path-b...
#Networking #Networking #L2 #VPC #DNS #Security
🎙️ Candidate Opening & Architectural Context
""Networking issues can paralyze distributed applications. In our hybrid cloud architecture, we traced this packet path. The interviewer is testing: OSI model, Layer 7 vs Layer 4, TLS termination.. 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
- ALB (Layer 7): Operates at the Application layer. It understands HTTP/HTTPS headers, URLs, and cookies. You use it when you need path-based routing (e.g.,
/apito one target group,/imagesto another), WebSocket support, or advanced WAF integrations. It terminates the connection and creates a new one to the backend. - NLB (Layer 4): Operates at the Transport layer. It only understands IP addresses and TCP/UDP ports. It is incredibly fast, handles millions of requests per second with ultra-low latency, and provides a static IP address. You use it for non-HTTP traffic (like databases, SSH, or custom TCP protocols) or when you require end-to-end TLS where the backend terminates the certificate.
2️⃣
Remediation & Permanent Safeguards
Execute the resolution runbook and verify workload health:
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: ALB (Layer 7): Operates at the Application layer. It understands HTTP/HTTPS headers, URLs, and cookies. You use it when you need p."
⚡ 60-Second Elevator Pitch Talking Points
- ALB (Layer 7): Operates at the Application layer. It understands HTTP/HTTPS headers, URLs, and co...
- NLB (Layer 4): Operates at the Transport layer. It only understands IP addresses and TCP/UDP port...
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