MongoDB Aggregation Pipeline

Build a MongoDB aggregation pipeline for [DATA ANALYSIS GOAL].

Collection: [COLLECTION NAME]
Sample document structure:
[PASTE SAMPLE JSON]

Required output: [DESCRIBE DESIRED RESULT]
Filters: [DATE RANGE/STATUS/etc.]

Create pipeline with:
- $match stage (indexed fields first)
- $lookup for joins if needed
- $group with accumulators
- $project to shape output
- Performance optimization tips
- Index recommendations