How do I avoid fetching more than needed from MongoDB?
Use projections to fetch only the fields you need. Instead of User.find() to get entire documents when you only need the name, use User.find({}, { name: 1, _id: 0 }) to get just the name field.
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More FAQs in Common MongoDB Mistakes in Node.js That Cause Performance Issues
Not adding indexes on frequently queried fields. Without indexes, every query scans the entire collection, which is slow as data grows. Add indexes for fields you query often, like email and userIds.
Fetching a list of items, then querying for each item's related data separately, causing N+1 queries instead of one. Use Mongoose populate to join related data in one query, avoiding the N+1 problem.
Fetching all documents at once uses too much memory and is slow for large lists. Use pagination with skip and limit, or cursor-based pagination with the id for better performance on large offsets.
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