Join Posts with Author Details Using $lookup

MongoDB

Technical Specification

Use aggregation pipeline with $lookup to fetch posts along with author name and email from users.

Input/Output Samples

Input:posts + users

Output:{ title, body, author: { name, email } }

Optimal Logic Path

db.posts.aggregate([
  {
    $lookup: {
      from: "users",
      localField: "userId",
      foreignField: "_id",
      as: "author",
    },
  },
  { $unwind: "$author" },
  {
    $project: {
      title: 1,
      body: 1,
      author: { name: "$author.name", email: "$author.email" },
    },
  },
]);

Architectural Deep-Dive

$lookup allows SQL-like joins between collections so you can combine posts and authors in one result.