Edge Rendering — Series 3

Preview — 3 of 10 questions

On an initial request to an App Router page, the server does more than one render pass before HTML reaches the browser. What is the pipeline?

AOne pass: components render straight to an HTML string

BPass 1 renders the React tree to the RSC payload (a serialized description of Server Component output plus references to Client Component modules and their props). Pass 2 (the SSR render) consumes that payload, renders the Client Components to HTML, and produces the final document. The same RSC payload is also embedded/streamed so the client can reconcile without a second data fetch

CThe client does all rendering; the server only sends JSON

DTwo identical React renders run for redundancy

What do stale, revalidate, and expire mean in a cacheLife profile?

javascript

// next.config.ts
const nextConfig = {
  experimental: {
    cacheLife: {
      catalog: { stale: 60, revalidate: 300, expire: 3600 },
    },
  },
};

AThey are three names for the same TTL

Bstale = server cache TTL; revalidate = browser cache TTL; expire = CDN TTL

Cstale is a delay before the first fetch; revalidate retries on error; expire is a hard timeout on the query

Dstale = how long a client may use a cached value before checking with the server; revalidate = how often the server refreshes the cached entry in the background; expire = the maximum age after which the value must not be served stale and a blocking refresh happens

What is the risk, and the mitigation?

javascript

User loads the app at 10:00 (deployment A). Leaves the tab open.
10:05 — you ship deployment B.
10:10 — the user submits a form whose Server Action ID was minted by deployment A.

AThe action ID is a stable hash of the action's module + name. If deployment B changed that action (or removed it), the old ID may not resolve on B's servers, causing the call to fail. Setting a consistent deploymentId (and/or skew protection that routes stale clients to the matching deployment) mitigates version skew

BNothing — action IDs are random per request and always valid

CThe action runs twice, once on each deployment

DThe browser automatically reloads to the new deployment before submitting

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