The Case of the Random 503: A CloudFront and Lambda@Edge Mystery
A client’s site returned intermittent HTTP 503s that were impossible to reproduce. The trail led to a Lambda@Edge origin-response function hitting a 3-second timeout on sequential cross-region calls to DynamoDB in us-east-1 and S3 in eu-west-1 — while executing in Asia Pacific. Here’s how CloudFront’s request path explains it.