I find myself back in Meteor-land recently, trying to track down queries with missing or lacking indexes. I find much of the tooling around tracking down these unindexed queries to be lacking, so I wrote a quick matb33:collection-hooks-based helper block to print out unindexed, or suspiscious queries in real time as they’re made by the Meteor application:

  [CollectionOne, "CollectionOne"],
  [CollectionTwo, "CollectionTwo"],
].forEach(([collection, name]) => {
  collection.before.find(function (userId, selector, options) {
      .find(selector, options)
      .then((res) => {
          `~~~ ${name}.find ${res?.queryPlanner?.winningPlan?.inputStage?.stage} ${res?.executionStats?.totalKeysExamined} ${res?.executionStats?.totalDocsExamined}`
        if (
          res?.queryPlanner?.winningPlan?.inputStage?.stage == "COLLSCAN" ||
          res?.executionStats?.totalKeysExamined > 2000 ||
          res?.executionStats?.totalDocsExamined > 2000
        ) {
          console.log(`!!! ${name} ${JSON.stringify(selector, null, 2)}`);

Just drop in the collection and their corresponding labels into the list above to explain query plans as they happen from your Meteor server.