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#data-transfer

2 stories

Banner: CDN cache bypassed because static assets carried Set-Cookie and private cache headers

Networking & DNS Bug Report

Origin egress doubled after a release: Set-Cookie made the CDN bypass its cache

Ryan Pham · Jun 10, 2026 · 5 min read

After a framework upgrade, our CDN cache hit ratio for static assets dropped from 97 to 41 percent and origin data transfer doubled. The new session middleware attached Set-Cookie and Cache-Control private to every response, including JavaScript bundles. Scoping middleware fixed it.

Banner: AWS cross availability zone data transfer costs from Kubernetes and Kafka traffic

Networking & DNS Bug Report

Cross-AZ data transfer quietly became our third biggest AWS cost

Ryan Pham · Mar 19, 2025 · 5 min read

DataTransfer-Regional-Bytes grew to 11,000 USD a month, behind only EC2 and RDS. Services spread across three zones talked to each other at random, and Kafka consumers read from leaders in other zones. Topology-aware routing and follower fetching cut it by 68 percent.