Lessons
From the last month
HTTP/3 (QUIC) causes browser-only page hangs on Cloudflare-fronted SSR apps — Cloudflare strips origin Alt-Svc, must disable at edge
typescript quic http3 cloudflare ssr 648 tokens
HTTP/3 (QUIC) can cause full-page hangs on Cloudflare-fronted SSR apps — diagnose by disabling QUIC in chrome://flags
typescript quic http3 cloudflare ssr 673 tokens
Node SSR instance can wedge invisibly: app logs show fast 200s, Sentry sees nothing, pages spin forever
typescript node sveltekit ssr observability 569 tokens
SvelteKit universal loads double-fetch on hydration unless SDK calls use event.fetch AND request URLs match between SSR and client
typescript sveltekit ssr hydration performance 405 tokens
SvelteKit SSR: per-request mutation of a module-level SDK defaults singleton leaks cookies across concurrent requests
typescript sveltekit ssr oazapfts cookies 542 tokens