eTag cache

Simple in-memory caching solution that supports revalidation via eTag and time-to-live (TTL).

Usage

import { ETagCache } from '@millihq/etag-cache';

async function revalidateHandler(key: string, eTag?: string) {
  if (eTag === '123') {
    // When the item of the cached item has not changed, you can simply return
    // the eTag and the expiration of the item in the cache gets updated.
    return {
      eTag: '123',
    };
  }

  return {
    item: 'bar',
    eTag: '123',
  };
}

const cache = ETagCache(60 /* TTL in seconds */, revalidateHandler);

const item = await cache.get('foo');
// => bar

Architecture

The cache is designed with a focus on reading performance. Expired items are only purged from the cache when new items are added to the cache.

sequenceDiagram
Client->>ETag Cache: get('foo')
ETag Cache->>TTL Cache: get('foo')
TTL Cache-->>ETag Cache: { item: 'bar', expired: true/false } | null
alt doesn't exist
  ETag Cache->>Client: Call revalidateHandler(key)
  Client-->>ETag Cache: { item: 'bar', eTag: '123' }
  ETag Cache->>TTL Cache: set('foo', 'bar')
else is expired
 ETag Cache->>Client: Call revalidateHandler(key, eTag)
 Client-->>ETag Cache: { eTag: '123' }
 ETag Cache->>TTL Cache: updateTTL('foo')
end
ETag Cache-->>Client: 'bar'

About

This project is maintained by milliVolt infrastructure.
We build custom infrastructure solutions for any cloud provider.

License

Apache-2.0 - see LICENSE for details.