Guidance for optimizing pipeline performance
Similar to any programming language, there is a downside if you prematurely optimize an aggregation pipeline. You risk producing an over-complicated solution that doesn't address the performance challenges that will manifest. As described in the previous section, the tool you should use to identify performance bottlenecks and opportunities for optimization is the explain plan. You will typically use the explain plan during the final stages of your pipeline's development once it is functionally correct.
With all that said, it can still help you to be aware of some guiding principles regarding performance while you are prototyping a pipeline. Critically, such guiding principles will be invaluable to you once the aggregation's explain plan is analyzed and if it shows that the current pipeline is suboptimal.
Be cognizant of streaming vs blocking stages ordering
When executing an aggregation pipeline, the database engine...
