redis_test.rb

subscriber_ids = Collection.find(4).likes.pluck(:user_id)
subscription = Subscription.find_by(source_identity: "4:collection")
id = subscription.id

def func1(subscriber_ids, id)
  Sider.subscription.with do |conn|
    subscriber_ids.each_slice(2000) do |batch|
      conn.pipelined do
        batch.each do |subscriber_id|
          conn.set("users:#{subscriber_id}:total_unread_subscriptions_count", 1)
          conn.hincrby("users:#{subscriber_id}:subscription_unread_count", id, 1)
        end
      end
    end
  end
end

def func2(subscriber_ids, id)
  Sider.subscription.with do |conn|
    subscriber_ids.each_slice(2000) do |batch|
      conn.pipelined do
        key_values = batch.flat_map { |subscriber_id| ["users:#{subscriber_id}:total_unread_subscriptions_count", 1] } 
        conn.mset(key_values)

        batch.each do |subscriber_id|
          conn.hincrby("users:#{subscriber_id}:subscription_unread_count", id, 1)
        end
      end
    end
  end
end

def func3(subscriber_ids, id)
  Sider.subscription.with do |conn|
    conn.pipelined do
      key_values = subscriber_ids.flat_map { |subscriber_id| ["users:#{subscriber_id}:total_unread_subscriptions_count", 1] } 
      conn.mset(key_values)

      subscriber_ids.each do |subscriber_id|
        conn.hincrby("users:#{subscriber_id}:subscription_unread_count", id, 1)
      end
    end
  end
end

Benchmark.bm do |x|
  x.report { func1(subscriber_ids, id) }
  x.report { func2(subscriber_ids, id) }
  x.report { func3(subscriber_ids, id) }
end