What the exam asks
- Choose ALB, NLB or GWLB from protocol, routing, IP and appliance requirements.
- Configure health checks, deregistration delay, stickiness, cross-zone load balancing and TLS handling.
- Design Auto Scaling groups across AZs with launch templates, the right health check type and mixed instance types.
- Choose target tracking, step, scheduled or predictive scaling, and the metric that represents load.
- Use lifecycle hooks and warm pools for slow start-up and clean shutdown.
Core ideas
Choosing the load balancer
| Application Load Balancer | Network Load Balancer | Gateway Load Balancer | |
|---|---|---|---|
| Layer and protocols | Layer 7: HTTP, HTTPS, gRPC, WebSockets | Layer 4: TCP, UDP, TLS | Layer 3: all IP traffic, over GENEVE on port 6081 |
| Routing | By path, host, header, query string, method or source IP. Also redirects, fixed responses and weighted target groups | By port and protocol, using a flow hash | To a fleet of virtual appliances, keeping each flow on the same appliance |
| Targets | Instances, IP addresses, Lambda functions | Instances, IP addresses, an ALB | Appliance instances or IP addresses |
| Static IPs | No (DNS name only) | One per AZ, which can be Elastic IPs | Not client-facing |
| Extras | Cognito/OIDC authentication, AWS WAF, SNI for many certificates | Ultra-low latency, very high request rates, client IP preserved, PrivateLink endpoint services | Transparent insertion of third-party firewalls and IDS/IPS through GWLB endpoints |
Decision rules:
- HTTP routing by path or host, authentication, WAF or Lambda targets ⇒ ALB.
- UDP, non-HTTP TCP, static or Elastic IPs, extreme performance or PrivateLink ⇒ .