Middleware

Middleware

Middleware wraps a store and returns another store that implements the same interface. This lets you add behavior like encryption or metrics without changing cache call sites.

Encryption middleware

createEncryptedStore() encrypts values before they are written and decrypts them on reads.

import {
  createCache,
  createEncryptedStore,
  createTTLStore,
  Time,
} from '@alexmchan/memocache'

const ttlStore = createTTLStore({ defaultTTL: 60 * Time.Second })

const encryptedStore = createEncryptedStore({
  key: 'this is secret sauce',
  salt: 'this is salty',
  store: ttlStore,
})

export const cache = createCache({
  stores: [encryptedStore],
})

Notes:

• key must be at least 8 characters
• changing key or salt changes the derived storage key and effectively invalidates old entries
• encryption uses the Web Crypto API, so runtime support matters

Metrics middleware

createMetricsStore() logs read, write, delete, and miss timings for a store.

import {
  createMetricsStore,
  createTTLStore,
  Time,
} from '@alexmchan/memocache'

const ttlStore = createTTLStore({ defaultTTL: 60 * Time.Second })

const metricsStore = createMetricsStore({
  store: ttlStore,
})

The emitted metrics include:

• cache.read
• cache.miss
• cache.write
• cache.delete

Each metric includes the key, store name, and measured latency.

Composition

Because middleware returns a store, you can layer it:

const store = createMetricsStore({
  store: createEncryptedStore({
    key: process.env.CACHE_KEY!,
    salt: process.env.CACHE_SALT!,
    store: createTTLStore({ defaultTTL: 5 * Time.Minute }),
  }),
})