CloudFront function or Lambda@edge

In terms of JWT validation, in my opinion you might want to consider CloudFront Functions as it provides the lowest possible latency with available free tier pricing.

Here's a quick comparison table in the document: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/edge-functions.html#edge-functions-choosing

Meanwhile, here's example CloudFront Functions that validates a JWT in the query string of a request which might be of help: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/example-function-validate-token.html

Another thing to consider is security. The CloudFront Function can't access KMS or Secrets Manager so you have to store the secret key in the source code. LambdaEdge will allow you to make use of purpose built secure storage to reduce the risk of key exposure. If you ever need to rotate the key, add a new key, etc. This is all a configuration change versus new code.