cacheMaxMemorySize

cacheMaxMemorySize sets the size, in bytes, of the in-memory cache each Next.js server instance keeps. It defaults to 50 MB.

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  cacheMaxMemorySize: 50 * 1024 * 1024, // 50 MB, the default
}

export default nextConfig

/** @type {import('next').NextConfig} */
const nextConfig = {
  cacheMaxMemorySize: 50 * 1024 * 1024, // 50 MB, the default
}

module.exports = nextConfig

The option sizes two separate caches:

• The server cache that stores prerendered pages, route handler responses, and optimized images. Set this to 0 when adopting a custom cacheHandler, so reads go to your store rather than a per-instance copy.
• The built-in handler behind 'use cache'. If you register your own handler through cacheHandlers, that handler manages its own memory and this option no longer applies to it.

Setting cacheMaxMemorySize: 0 disables both in-memory caches. It is also a way to mimic how use cache behaves in a serverless environment, where entries rarely survive between requests.

Good to know: next dev keeps its own in-memory cache regardless of this option, so reloads stay fast. Production honors the configured value exactly.