Supplementary code for this article: https://engineering.mrsool.co/using-redis-hashes-for-caching-in-ruby-on-rails-6dc53df293da

redis_hash_store.rb

module RedisHashStore
  extend self

  class Entry
    attr_reader :value

    def initialize(value, expires_in:)
      @value = value
      @created_at = Time.now.to_f
      @expires_in = expires_in
    end

    def expired?
      @expires_in && @created_at + @expires_in <= Time.now.to_f
    end
  end

  def write(hash_key, sub_key, value, **options)
    entry = Entry.new(value, expires_in: options[:expires_in])
    redis.hset(hash_key, sub_key, serialize_value(entry))

    entry.value
  end

  def read(hash_key, sub_key)
    entry = deserialize_value(redis.hget(hash_key, sub_key))

    return if entry.blank?

    if entry.expired?
      delete(hash_key, sub_key)

      return nil
    end

    entry.value
  end

  def delete(hash_key, sub_key)
    redis.hdel(hash_key, sub_key)
  end

  def delete_hash(hash_key)
    redis.del(hash_key)
  end

  private

  def serialize_value(value)
    Marshal.dump(value)
  end

  def deserialize_value(value)
    return if value.nil?

    Marshal.load(value)
  end

  def redis
    Rails.cache.redis
  end
end