Paul Graham inspired the creation of Redis(twitter.com)

  class EventStore {
    constructor(file) {
      this.file = file;
      this.cache = null;
    }
  
    async appendEvent(event) {
      // Purge the cache for entries since we mutated the store.
      this.cache = null;
      return new Promise((resolve, reject) => {
        createWriteStream(this.file, { flags: 'a' })
          .on('error', reject)
          .on('close', resolve)
          .end(`${JSON.stringify(event)}\n`);
      });
    }

    async readEvents() {
      if (this.cache !== null) {
        return this.cache;
      }

      try {
        const data = await readFile(this.file, 'utf-8');
        const lines = data.split('\n').filter(line => line);
        const events = lines.map(line => JSON.parse(line));
        this.cache = events;
        return events;
      } catch (error) {
        return [];
      }
    }
  }