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AWS Lambda Function URLs: CORS configuration, HTTP API versus REST API, and auth with IAM or none
Function URLs expose a dedicated HTTPS endpoint—set `AllowOrigins` in the URL config, not only in API Gateway stages.
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awslambdacors
Provisioned concurrency
Warm pools reduce cold OPTIONS latency—monitor p99 separately from API Gateway routes.
Reserved concurrency limits can throttle preflight under burst traffic.
VPC
Lambda in a VPC may call private APIs—CORS still terminates at the public URL facing browsers.
NAT gateway costs spike when SPAs retry CORS-heavy flows—alert on retry ratios.