What is the route segment config in Next.js (dynamic, revalidate, runtime)?

Q: What is the route segment config in Next.js (dynamic, revalidate, runtime)?

**Target Audience:** Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity. **Difficulty:** Medium > **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:`. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the **Verified** section, against real output from a build or a running server; each Verified block names the version it ran on. ## 1. Why This Even Matters — A Story First Segment config is the settings panel on the back of each room in a building: lights always on, lights on a timer, which power supply to use, how long a machine may run. Next.js 16 rewired the building: the light switches (caching) moved into the rooms themselves as 'use cache', and the special low-power supply (edge) is being retired. The panel still exists, but with fewer switches. ## 2. The Core Idea 📌 **Interview

The problem

Question presented to candidate: "What are the export const options you can put in a page, layout or route file, what do dynamic, revalidate and runtime do, and what changed in Next.js 16?"

What a strong answer should cover:

Segment config is a set of named exports in a page, layout or Route Handler that tune how that segment is rendered.
The classic set: dynamic, dynamicParams, revalidate, fetchCache, runtime, preferredRegion, maxDuration.
dynamic forces static or dynamic rendering ('force-dynamic', 'force-static', 'error'); revalidate sets the ISR lifetime.
In Next.js 16, with Cache Components enabled, dynamic, dynamicParams, revalidate and fetchCache are removed (the build rejects them); caching moves to 'use cache' and cacheLife.
runtime = 'edge' and preferredRegion are deprecated in 16; the default Node.js runtime is the recommendation. With Cache Components any runtime export must go, even 'nodejs', and 16.4 adds ensureStatic to require a page or layout to stay static.

Clarifying questions expected:

"Is Cache Components enabled in this project?" — it changes which exports are allowed.
"Is the goal caching, timing, or hosting?" — different options serve each.

Code / implementation expected: Yes — the common exports and their Next.js 16 replacements.

nextjs
segment-config
revalidate
runtime

Try it yourself

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Solution

Target Audience: Frontend engineers preparing for Next.js interviews — assumes basic React and App Router familiarity. Difficulty: Medium

How to read this doc: Each idea is explained in plain language first, then tagged with 📌 Interview term:. Every behaviour claim was checked against the Next.js docs shipped with the package (written on 16.3.4, re-reviewed against 16.4.2) and, in the Verified section, against real output from a build or a running server; each Verified block names the version it ran on.

1. Why This Even Matters — A Story First

Segment config is the settings panel on the back of each room in a building: lights always on, lights on a timer, which power supply to use, how long a machine may run. Next.js 16 rewired the building: the light switches (caching) moved into the rooms themselves as 'use cache', and the special low-power supply (edge) is b

The solution is hidden so you can try first

5 min read · 8 sections

Read the code

Common exports, and the Cache Components replacement

// Previous model (cacheComponents off)
export const revalidate = 600;            // ISR lifetime for this route
export const dynamic = "force-static";    // or "force-dynamic" / "error"
export const maxDuration = 30;            // platform limit for server work
// With cacheComponents (16.4+): export const ensureStatic = "navigation"; requires fully static output

// With cacheComponents: true, drop dynamic/revalidate and cache the data instead:
import { cacheLife } from "next/cache";
async function getCatalogue() {
  "use cache";
  cacheLife("minutes");
  return db.product.findMany();
}

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