Sharding implications for pipelines

MongoDB sharding isn't just an effective way to scale out your database to hold more data and support higher transactional throughput. Sharding also helps you scale out your analytical workloads, potentially enabling aggregations to be completed far quicker. Depending on the nature of your aggregation and some adherence to best practices, the cluster may execute parts of the aggregation in parallel over multiple shards for faster completion.

There is no difference between a replica set and a sharded cluster regarding the functional capabilities of the aggregations you build, except for a minimal set of constraints. The sharded aggregation constraints section in this chapter will outline these constraints. When it comes to optimizing your aggregations, in most cases, there will be little to no difference in the structure of a pipeline when refactoring for performance on a sharded cluster compared to a simple replica set.

You should always...