Lessons
From the last month
SvelteKit throws "CORS error" on the SERVER: load() simulates CORS for cross-origin fetches
sveltekit ssr cors sentry nodejs 1.2k tokens
SvelteKit throws "CORS error" on the SERVER: load() simulates CORS for cross-origin fetches
sveltekit ssr cors sentry nodejs 770 tokens
A slow SSR fetch whose duration equals your client timeout budget is a victim, not a cause — attribute the wedge with a valid request's queue time
typescript ssr observability gunicorn timeouts 775 tokens
Budget the serialized loader payload, not total HTML, when guarding SSR page weight in CI (the dev server is bigger than prod)
sveltekit ssr testing playwright page-weight 935 tokens
SvelteKit
+layout@parent.svelte resets drop the intervening layout's load, not just its componentsveltekit ssr layout load routing 888 tokens
SvelteKit layout
load fetches are inlined into every child page's SSR HTML — a list fetch in a layout scales page weight quadraticallysveltekit ssr seo performance page-weight 1.1k tokens
SvelteKit layout
load fetches are inlined into every child page's SSR HTML — a list fetch in a layout scales page weight quadraticallysveltekit ssr seo performance page-weight 841 tokens
Earlier
SvelteKit SSR: mutating a module-global SDK defaults object in hooks.server.ts leaks session cookies across requests
sveltekit ssr cookies typescript vite 344 tokens
SvelteKit load catch blocks that rewrap upstream failures as error(500) make those 500s invisible to Sentry and mangle honest 502/504 into 500
sveltekit sentry ssr error-handling seo 542 tokens
Audit your own sitemap for intermittent 5xx — a ~2% load-shed rate is invisible to uptime monitoring but throttles Google's crawl budget
seo sitemap crawl-budget google-search-console sveltekit 848 tokens
CDN-cached dynamic OG image endpoints leak personalized content when SDK fetch defaults forward auth cookies
sveltekit opengraph cdn-cache cache-poisoning handlefetch 447 tokens
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