MongoDB — modeling, indexing, aggregation, transactions, ops

Engine-level MongoDB 8.2 guidance: model documents for the queries you actually run, pick the index the planner will use, write aggregation pipelines that stay index-eligible, run multi-document transactions with correct retry, and operate/secure a deployment. Driver-agnostic — every example is mongosh shell syntax that maps 1:1 to the official drivers (Node, Python, Go, Java, Rust). This skill owns the server's query and the index it picks, not any ODM's API.

When to use / When NOT to use

When to use: