High Performance Next.js 15 Caching and a Replacement for unstable_cache

Thanks in part to the movement towards 'servers' in JavaScript frameworks like Next.js 15 , Remix (now React Router 7)  and Tanstack Start  - there's an increased interest server-side caching strategies. In our case we wanted a server-based cache that was framework agnostic, as well as a replacement for Next.js 15 unstable_cache .

We also wanted a 'tagging' system - a bit like Drupal's cache, and others, as well as an in-memory cache that would support clustered machines at Fly.io 

We based our solution on Cacheable  and CacheManager  - an excellent project from Jared Wray .

Here's our CacheManager singleton (yes yes we know - singletons are bad. Use this instead - Awilix ).

cache-manager.ts

import { Cache, createCache as createCacheManager } from 'cache-manager'
import { Keyv } from 'keyv'
import { KeyvCacheableMemory } from 'cacheable'

const createCache = (): Cache => {
  // ttl = 60 seconds
  // lruSize = 5000 the number of LRU cache entries
  // For example, if each cache item was 50KB, and all
  // 5000 keys were used - we would store 250MB of data.
  const store = new KeyvCacheableMemory({ ttl: 60000, lruSize: 5000 })
  const keyv = new Keyv({ store })
  return createCacheManager({ stores: [keyv] })
}

let cacheManager: Cache | undefined

export const getCacheManager = (): Cache => {
  cacheManager ??= createCache()
  return cacheManager
}

Next, our tags-manager.ts

import type { Cache } from 'cache-manager'


export interface CacheWithTags {
  store(key: string, data: any, options?: { ttl?: number; tags?: string[] }): Promise<void>
  wrap<T, Args extends unknown[]>(
    key: string,
    fn: (...args: Args) => Promise<T>,
    options?: { ttl?: number; refreshThreshold?: number; tags?: string[] }
  ): Promise<T>
  retrieve(key: string): Promise<any | null>
  invalidateTag(tag: string): Promise<void>
  invalidateKey(key: string): Promise<void>
  clear(): Promise<true>
}


export class TagsManager implements CacheWithTags {
  private cache: Cache
  private keyToTagsMap: Map<string, Set<string>>


  constructor(cache: any) {
    this.cache = cache
    this.keyToTagsMap = new Map() // In-memory key-to-tags mapping, not persisted across application restarts
  }


  // Helper method to add tags to a key's tag list
  private _addTagsToKey(key: string, tags?: string[]): void {
    if (tags == null) return
    if (this.keyToTagsMap.has(key) === false) {
      this.keyToTagsMap.set(key, new Set())
    }
    const keyTags = this.keyToTagsMap.get(key)
    const uniqueTags = new Set(tags) // Ensure unique tags
    uniqueTags.forEach((tag) => keyTags?.add(tag))
  }


  // Helper method to remove tags from a key's tag list
  private _removeTagsFromKey(key: string): void {
    this.keyToTagsMap.delete(key)
  }


  // Store data in cache with key, data, and options
  async store(key: string, data: any, options?: { ttl?: number; tags?: string[] }): Promise<void> {
    const { ttl, tags } = options || {}
    // Map the key to the provided tags
    this._addTagsToKey(key, tags)
    // Save the data in the cache
    await this.cache.set(key, data, ttl)
  }


  // Wrap method to manage cacheable operations
  async wrap<T, Args extends unknown[]>(
    key: string,
    fn: (...args: Args) => Promise<T>,
    options?: { ttl?: number; refreshThreshold?: number; tags?: string[] }
  ): Promise<T> {
    const { ttl, refreshThreshold, tags } = options || {}
    // Map the key to the provided tags
    this._addTagsToKey(key, tags)
    return await this.cache.wrap(key, fn, ttl, refreshThreshold)
  }


  // Retrieve data from cache by key
  async retrieve(key: string): Promise<any | null> {
    return await this.cache.get(key)
  }


  // Invalidate cache by tag or key
  async invalidateTag(tag: string): Promise<void> {
    // Invalidate all keys associated with a tag
    const keysToInvalidate = Array.from(this.keyToTagsMap.entries())
      .filter(([, tags]) => tags.has(tag))
      .map(([cacheKey]) => cacheKey)


    for (const cacheKey of keysToInvalidate) {
      await this.cache.del(cacheKey)
      const tags = this.keyToTagsMap.get(cacheKey)
      tags?.delete(tag)
      if (tags?.size === 0) {
        this.keyToTagsMap.delete(cacheKey)
      }
    }
  }


  // Invalidate cache by tag or key
  async invalidateKey(key: string): Promise<void> {
    // Invalidate a specific key and clean up tag mappings
    await this.cache.del(key)
    this._removeTagsFromKey(key)
  }


  async clear(): Promise<true> {
    await this.cache.clear()
    this.keyToTagsMap.clear()
    return true
  }
}

And now for the magic. Fly.io makes it very easy to retrieve all of the IP addresses for all of the machines serving your application - see Fly.io private networking  for more. And so I present to you - cluster-manager.ts (I know what you're thinking).

import { Resolver } from 'dns'
import { stdSerializers } from 'pino'
import { getConfig } from '../../config'
import { getLogger } from '../logger'

export async function resolveInternalDNS(): Promise<{ ipv6Addresses: string[] }> {
  const config = getConfig()
  const domain = config.privateNetworkDomain

  // Create a custom DNS resolver
  const resolver = new Resolver()
  resolver.setServers(['[fdaa::3]']) // Use Fly.io's custom DNS server

  return new Promise((resolve, reject) => {
    resolver.resolve6(domain, (err, addresses) => {
      if (err) {
        return reject(err)
      }
      resolve({ ipv6Addresses: addresses })
    })
  })
}

export async function invalidateClusterCacheTag(tag: string) {
  return await invalidateClusterCache(tag, 'tag')
}

export async function invalidateClusterCacheKey(key: string) {
  return await invalidateClusterCache(key, 'key')
}

export async function invalidateClusterCache(
  value: string,
  type: 'tag' | 'key'
): Promise<{ ip: string; status: 'success' | 'failed' | 'idle'; data?: any; error?: string }[]> {
  const config = getConfig()
  const logger = getLogger()
  const endpoint = '/someroute/on-every-machine'
  const port = config.privateNetworkApplicationPort
  const results: {
    ip: string
    status: 'success' | 'failed' | 'idle'
    data?: any
    error?: string
  }[] = []

  try {
    const { ipv6Addresses } = await resolveInternalDNS()
    if (ipv6Addresses == null || ipv6Addresses.length === 0) {
      logger.error({
        cluster_cache: {
          status: 'failed',
          message: 'no ipv6 addresses found via resolveInternalDNS in clusterInvalidateCache',
          method: 'clusterInvalidateCache'
        }
      })
      results.push({
        ip: 'unknown',
        status: 'failed',
        error: 'no ipv6 addresses found via resolveInternalDNS in clusterInvalidateCache'
      })
    }

    for (const ip of ipv6Addresses) {
      const queryString = type === 'tag' ? `tag=${value}` : `key=${value}`
      const url = `http://[${ip}]:${port}${endpoint}?${queryString}` // Format the URL for IPv6

      try {
        const response = await fetch(url)
        if (response.ok) {
          const data = await response.json()
          logger.info({
            cluster_cache: {
              status: 'success',
              message: 'clusterInvalidateCache successfully called',
              data,
              method: 'clusterInvalidateCache'
            }
          })
          results.push({ ip, status: 'success', data })
        } else {
          logger.error({
            cluster_cache: {
              status: 'failed',
              message: 'response not okay clusterInvalidateCache',
              method: 'clusterInvalidateCache',
              error: `HTTP ${response.status} ${response.statusText}`
            }
          })
          results.push({
            ip,
            status: 'failed',
            error: `HTTP ${response.status} ${response.statusText}`
          })
        }
      } catch (error) {
        logger.error({
          cluster_cache: {
            status: 'failed',
            message: 'error in clusterInvalidateCache',
            method: 'clusterInvalidateCache',
            error: stdSerializers.err(error as Error)
          }
        })
        results.push({
          ip,
          status: 'failed',
          error: error instanceof Error ? error.message : 'Unknown error'
        })
      }
    }
  } catch (error) {
    logger.error({
      cluster_cache: {
        status: 'failed',
        message: 'error resolving DNS in clusterInvalidateCache',
        method: 'clusterInvalidateCache',
        error: stdSerializers.err(error as Error)
      }
    })
    results.push({
      ip: 'unknown',
      status: 'failed',
      error: 'error resolving DNS in clusterInvalidateCache'
    })
  }

  return results
}

If we've enabled our cluster cache option - calling invalidateKey or invalidateTag below - will send an HTTP request to an API route handler available on every machine in our application - which will in turn call the correct cache invalidate function for the local in-memory cache.

Here's the top-level cache adapter that takes care of all of the above.

cache.ts

import { getConfig } from '../../config'
import { TagsManager, CacheWithTags } from './tags-manager'
import { getCacheManager } from './cache-manager'
import { invalidateClusterCacheTag, invalidateClusterCacheKey } from './cluster-manager'

const createTagsManager = (): CacheWithTags => {
  const cache = getCacheManager()
  return new TagsManager(cache)
}

let cache: CacheWithTags | undefined

export const getCache = (): CacheWithTags => {
  cache ??= createTagsManager()
  return cache
}

export async function store(
  key: string,
  data: any,
  options?: { ttl?: number; tags?: string[] }
): Promise<void> {
  const cache = getCache()
  await cache.store(key, data, options)
}

export function storeFunction<T, Args extends unknown[]>(
  key: string,
  fn: (...args: Args) => Promise<T>,
  options?: { ttl?: number; refreshThreshold?: number; tags?: string[] }
): (...args: Args) => Promise<T> {
  const cache = getCache()

  // Return a function that accepts the arguments for `fn`
  return async (...args: Args): Promise<T> => {
    // Use the internal cache.wrap method
    return await cache.wrap(key, () => fn(...args), options)
  }
}

export async function retrieve(key: string): Promise<any | null> {
  const cache = getCache()
  return await cache.retrieve(key)
}

export async function invalidateTag(tag: string): Promise<void> {
  const config = getConfig()
  if (config.cachingClusterEnabled === true) {
    await invalidateClusterCacheTag(tag)
  } else {
    const cache = getCache()
    await cache.invalidateTag(tag)
  }
}

export async function invalidateKey(key: string): Promise<void> {
  const config = getConfig()
  if (config.cachingClusterEnabled === true) {
    await invalidateClusterCacheKey(key)
  } else {
    const cache = getCache()
    await cache.invalidateKey(key)
  }
}

export async function clear(): Promise<true> {
  const cache = getCache()
  return await cache.clear()
}

And after all of that, if we want to cache data (with a key and tags) in our data access layer, for example, in calling the Payload CMS  local API to get a list of documents - we can do something like this...

export async function getStories(locale: string): Promise<StoriesResponse> {
  const config = getConfig()
  if (config.cachingDataRequests === true) {
    const cacheKey = `stories-list::${locale}`
    const cacheTag = `cms::stories`
    return storeFunction(cacheKey, getStoriesFn, {
      tags: [cacheTag]
    })(locale, null)
  } else {
    return getStoriesFn(locale, null)
  }
}

Inside getStoriesFn we call payload.find.

Enjoy!