Q: What is an Elastic Load Balancer and what are the differences between ALB, NLB, and CLB?
- CLB (Classic Load Balancer) — legacy. Avoid for new projects. Layer 4 and Layer 7 but limited features.
#AWS #Networking & VPC #L2 #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
Choose: ALB for web apps/APIs. NLB for TCP/UDP or when you need static IP. GWLB for network security appliances.
- CLB (Classic Load Balancer) — legacy. Avoid for new projects. Layer 4 and Layer 7 but limited features.
- ALB (Application Load Balancer) — Layer 7 (HTTP/HTTPS). Content-based routing: route by URL path, hostname, headers, query strings. Best for microservices and HTTP apps. Supports WebSockets, HTTP/2.
- NLB (Network Load Balancer) — Layer 4 (TCP/UDP/TLS). Ultra-low latency. Handles millions of requests per second. Static IP / Elastic IP support. Best for high-performance, non-HTTP workloads (game servers, IoT, VoIP).
2️⃣
Remediation & Permanent Safeguards
- GWLB (Gateway Load Balancer) — for inline network appliances (firewalls, IDS/IPS). Newer addition.
💡 The Senior SRE Gold Nugget (Key Architectural Takeaway)
"Pro-Tip: CLB (Classic Load Balancer) — legacy. Avoid for new projects. Layer 4 and Layer 7 but limited features.."
⚡ 60-Second Elevator Pitch Talking Points
- CLB (Classic Load Balancer) — legacy. Avoid for new projects. Layer 4 and Layer 7 but limited fea...
- ALB (Application Load Balancer) — Layer 7 (HTTP/HTTPS). Content-based routing: route by URL path,...
- NLB (Network Load Balancer) — Layer 4 (TCP/UDP/TLS). Ultra-low latency. Handles millions of reque...
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