Cache

Cached event handlers

To cache an event handler, you simply need to use the defineCachedEventHandler method.

It works like defineEventHandler but with an additional second options parameter.

// Cache an API handler
export default defineCachedEventHandler((event) => {
  // My event handler
}, { maxAge: 60 * 60 /* 1 hour */ });

With this example, the response will be cached for 1 hour and a stale value will be sent to the client while the cache is being updated in the background. If you want to immediately return the updated response set swr: false.

See the options section for more details about the available options.

Cached functions

You can also cache a function using the defineCachedFunction function. This is useful for caching the result of a function that is not an event handler, but is part of one, and reusing it in multiple handlers.

For example, you might want to cache the result of an API call for one hour:

export const cachedGHStars = defineCachedFunction(async (repo: string) => {
  const data: any = await $fetch(`https://api.github.com/repos/${repo}`)

  return data.stargazers_count
}, {
  maxAge: 60 * 60,
  name: 'ghStars',
  getKey: (repo: string) => repo
})

export default defineEventHandler(async (event) => {
  const repo = event.context.params.repo
  const stars = await cachedGHStars(repo).catch(() => 0)

  return { repo, stars }
})

The stars will be cached in development inside .nitro/cache/functions/ghStars/<owner>/<repo>.json with value being the number of stars.

{"expires":1677851092249,"value":43991,"mtime":1677847492540,"integrity":"ZUHcsxCWEH"}

Edge workers

In edge workers, the instance is destroyed after each request. Nitro automatically uses event.waitUntil to keep the instance alive while the cache is being updated while the response is sent to the client.

To ensure that your cached functions work as expected in edge workers, you should always pass the event as the first argument to the function using defineCachedFunction.

import type { H3Event } from 'h3'

export const cachedGHStars = defineCachedFunction(async (event: H3Event, repo: string) => {
  const data: any = await $fetch(`https://api.github.com/repos/${repo}`)

  return data.stargazers_count
}, {
  maxAge: 60 * 60,
  name: 'ghStars',
  getKey: (event: H3Event, repo: string) => repo
})

export default defineEventHandler(async (event) => {
  const repo = event.context.params.repo
  const stars = await cachedGHStars(event, repo).catch(() => 0)

  return { repo, stars }
})

This way, the function will be able to keep the instance alive while the cache is being updated without slowing down the response to the client.

Caching route rules

This feature enables you to add caching routes based on a glob pattern directly in the main configuration file. This is especially useful to have a global cache strategy for a part of your application.

Cache all the blog routes for 1 hour with stale-while-revalidate behavior:

export default defineNitroConfig({
  routeRules: {
    "/blog/**": { cache: { maxAge: 60 * 60 } },
  },
});

export default defineNuxtConfig({
  routeRules: {
    "/blog/**": { cache: { maxAge: 60 * 60 } },
  },
});

If we want to use a custom storage mount point, we can use the base option.

export default defineNitroConfig({
  storage: {
    redis: {
      driver: "redis",
      url: "redis://localhost:6379",
    },
  },
  routeRules: {
    "/blog/**": { cache: { maxAge: 60 * 60, base: "redis" } },
  },
});

export default defineNuxtConfig({
  nitro: {
    storage: {
      redis: {
        driver: "redis",
        url: "redis://localhost:6379",
      },
    },
  },
  routeRules: {
    "/blog/**": { cache: { maxAge: 60 * 60, base: "redis" } },
  },
});

Customize cache storage

Nitro stores the data in the cache: mount point.

• In production, it will use the memory driver by default.
• In development, it will use the filesystem driver, writing to a temporary dir.

To overwrite the production storage, set the cache mount point using the storage option:

export default defineNitroConfig({
  storage: {
    cache: {
      driver: 'redis',
      /* redis connector options */
    }
  }
})

export default defineNuxtConfig({
  nitro: {
    storage: {
      cache: {
        driver: 'redis',
        /* redis connector options */
      }
    }
  }
})

In development, you can also overwrite the cache mount point using the devStorage option:

export default defineNitroConfig({
  devStorage: {
    cache: {
      driver: 'redis',
      /* redis connector options */
    }
  }
})

export default defineNuxtConfig({
  nitro: {
    devStorage: {
      cache: {
        driver: 'redis',
        /* redis connector options */
      }
    }
  }
})

Options

The cachedEventHandler and cachedFunction functions accept the following options:

Cache keys and invalidation

When using the defineCachedFunction or defineCachedEventHandler functions, the cache key is generated using the following pattern:

`${options.group}:${options.name}:${options.getKey(...args)}.json`

For example, the following function:

const getAccessToken = defineCachedFunction(() => {
  return String(Date.now())
}, {
  maxAge: 10,
  name: 'getAccessToken',
  getKey: () => 'default'
})

Will generate the following cache key:

nitro:functions:getAccessToken:default.json

You can invalidate the cached function entry with:

await useStorage('cache').removeItem('nitro:functions:getAccessToken:default.json')

Normalizing Cache Keys

For example:

getKey: () => '/api/products/sale-items'

Would generate a key like:

api/productssaleitems.json

This behavior may result in keys that look different from the original route or identifier.

function escapeKey(key: string | string[]) {
  return String(key).replace(/\W/g, "");
}

It's recommended to use escapeKey() when invalidating manually using route paths or identifiers to ensure consistency with Nitro's internal key generation.

For example, if your getKey function is:

getKey: (id: string) => `product/${id}/details`

And you want to invalidate product/123/details, you would do:

const normalizedKey = escapeKey('product/123/details')
await useStorage('cache').removeItem(`nitro:functions:getProductDetails:${normalizedKey}.json`)