How to optimize background processes? Sylius meets Blackfire

With the recent Sylius release v1.11, we've introduced a brand new feature - catalog promotions. As this feature may require processing a significant amount of data(the whole product catalog), we had to decide on async processing by default. But it does not mean that we can waste resources and not optimize the processing algorithm! We had to improve it and to do that we've been using Blackfire.