Route 53

• EC2 cannot be a pointed to by an Alias record
• Primary record must have health check for failover routing policy
• Failure Threshold is the parameter used by Route 53 health checks to determine if an endpoint is healthy. A failure occurs if an endpoint does not respond to a request.
• Route 53 can be used as a DNS to register a domain name, route the internet traffic, and perform health checks on resources. If being used for all three tasks, the order of setup must be sequential as above.

ELB

• ELB has access logs
• ALB, NLB and CloudFront support SNI
• Session affinity is only supported by CLB and ALB (layer 7)

API Gateway

• For HTTP_PROXY integration type, option to add HTTP headers in the request (eg. API key)
• Mapping template uses Velocity Template Language (VTL)
• Private endpoints can only be accessed within your VPC using an Interface VPC endpoint (ENI)
• TTL: 0 s - 1 h (default 300 sec)
• Two types of logs:
  • Execution Logs: log requests, responses, etc.
  • Access Logs: who accessed the API and how
• When the integration type is proxy-based, the responses are proxied to the client without modification by API gateway. So, CORS needs to be handled by the backend itself.
• MaxAgeSeconds specifies the TTL used by browser to cache pre-flight response
• Associate API stages and API keys with the usage plan using CreateUsagePlanKey API

ECS