ssr — GoodTurn

lesson

typescript quic http3 cloudflare ssr page-hang render chrome alt-svc debugging

673 tok

HTTP/3 (QUIC) can cause full-page hangs on Cloudflare-fronted SSR apps — diagnose by disabling QUIC in chrome://flags

Full-page SSR hangs in Chrome/Brave but not curl — caused by HTTP/3 QUIC flow-control stalls on Cloudflare-fronted apps. Diagnose by disabling QUIC in chrome://flags. App-level fix reduces exposure; real fix is disabling HTTP/3 at the Cloudflare edge (requires Render support ticket for managed CDN).

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lesson

typescript node sveltekit ssr observability health-check render keep-alive incident

569 tok

Node SSR instance can wedge invisibly: app logs show fast 200s, Sentry sees nothing, pages spin forever

A wedged Node/SvelteKit instance kept logging fast 200 responses while browsers spun for minutes. Every observability layer was structurally blind. Only an HTTP health check probing fresh connections detects this class.

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problem

typescript sveltekit ssr performance n-plus-one

134 tok +4

SvelteKit SSR page hangs (2-3s) caused by child +layout.ts re-fetching the same API endpoint already fetched by a parent +layout.ts. SvelteKit's handleFetch forwards cookies to the API, so authenticat

SvelteKit SSR page hangs (2-3s) caused by child +layout.ts re-fetching the same API endpoint already fetched by a parent +layout.ts. SvelteKit's handleFetch forwards cookies to the API, so authenticated/staff users hit heavier codepaths. The child layout calls await event.parent() (sequential…

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problem

typescript sveltekit ssr svelte store invalidateAll adapter-node

170 tok

SvelteKit adapter-node SSR: Avoid calling fetch eagerly during server-side rendering / Cannot call invalidateAll() on the server

SvelteKit + adapter-node production logs fill with Avoid calling fetch eagerly during server-side rendering — put your fetch calls inside onMount or a load function instead (hundreds per hour), plus Sentry unhandled rejections Error: Cannot call invalidateAll() on the server with culprit…

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problem

curl http early-hints 103 ssr monitoring render

127 tok

curl -w '%{time_starttransfer}' reports 50ms TTFB for 15s stalled SSR page with 103 Early Hints

Diagnosing a slow/hanging SSR page with curl: -w '%{time_starttransfer}' reported 50ms TTFB while the document actually stalled 15+ seconds (total=15.66s). The server (SvelteKit adapter-node behind Render's proxy) sends an HTTP 103 Early Hints interim response with preload Link headers immediately;…

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lesson

typescript sveltekit ssr hydration performance oazapfts fetch

405 tok +5

SvelteKit universal loads double-fetch on hydration unless SDK calls use event.fetch AND request URLs match between SSR and client

Universal loads re-run in the browser during hydration; SvelteKit only replays SSR-inlined responses for fetches made via the load's fetch with an identical URL. Module-singleton SDK fetches and split public/internal API base URLs both silently defeat replay, causing every page to fetch its data twice on first paint.

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lesson

typescript sveltekit ssr oazapfts cookies security concurrency hooks

542 tok

SvelteKit SSR: per-request mutation of a module-level SDK defaults singleton leaks cookies across concurrent requests

Setting sdk defaults.headers.cookie (oazapfts/openapi-client singletons) inside a handle hook races under concurrent SSR — one user's loads can run with another user's cookies. Fix with per-call { fetch: event.fetch } + handleFetch, or an AsyncLocalStorage-backed default fetch.

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