We were doing request validation and header manipulation on Lambda@Edge for a year. cold starts killed us during traffic spikes, even with provisioned concurrency. switched to CloudFront functions last spring and never looked back.

CloudFront functions run inline, no cold starts, sub-millisecond latency. the tradeoff is they're limited to 10KB code and no external calls, but honestly that covers 95% of what we were doing anyway. request signing, geo blocking, cache key manipulation.

Lambda@Edge for heavy lifting still makes sense. but if you're just doing request/response transforms, cloudfront functions are the obvious pick. way simpler, faster, cheaper.