mongodb-find-queries_skill

Overview

This skill teaches mastering MongoDB find queries with practical patterns for filters, projections, sorting, and pagination. It focuses on real-world examples, common operators, and performance tips so you can retrieve the right documents efficiently. The content is practical, language-agnostic in approach, and demonstrated with common JavaScript/Python-friendly patterns.

How this skill works

The skill inspects and explains the find() method, covering comparison, logical, array and regex operators, plus text search and nested document queries. It shows how to shape results with projection, order with sort/collation, and paginate with skip/limit or cursor-based techniques. The material also highlights query optimization practices such as indexing, early filtering, limiting fields, and using explain().

When to use it

• When you need to retrieve specific documents using filters and operators
• When you must return a subset of fields to reduce payload (projection)
• When results need ordering, case-insensitive collation, or multi-field sorts
• When implementing pagination for web APIs or large result sets
• When building text search, regex search, or nested/document-specific queries

Best practices

• Create indexes on frequently filtered and sorted fields to avoid collection scans
• Filter early and narrow results before expensive operations or projections
• Project only required fields to reduce bandwidth and memory use
• Prefer cursor-based pagination (range queries on indexed keys) for large datasets
• Use explain() to inspect query plans and fix slow queries
• Avoid unbounded find({}) calls without limit or proper filtering

Example use cases

• User search endpoint: regex name/email search, exclude passwords, paginate results
• Product listing: combine price range, category filter, sorting and limit for UI pages
• Feed or timeline: cursor-based pagination using _id or timestamp for consistent traversal
• Analytics queries: date-range filters on createdAt with proper index usage
• Admin tools: nested document queries (address.city) and existence/null checks