Sorting Results

Introduction

Sort orders the cursor. The trick: sorting on an unindexed field forces an in-memory sort, which is capped at ~32 MB and will error out for large result sets. Always sort on an index.

Syntax reference

db.posts.find().sort({ createdAt: -1 }).limit(20);

Real-world use

Every 'newest first' or 'top liked' list relies on indexed sort.

Best practices

• Match sort key with an index (compound is fine).
• Combine filter + sort fields in one compound index.

Common mistakes

• In-memory sort fails over 32 MB — check explain.