Before MongoDB 3.6, tailing the MongoDB oplog was the only way to listen for changes to your MongoDB database. The oplog is a special collection that logs all inserts and updates that come in to your MongoDB server so other members of the replica set can copy them. Tools like Meteor and MoSQL were built on tailing the oplog. Unfortunately, the oplog was built primarily to support replication internally as opposed to being a user-facing feature. Change streams are a usability layer on top of the MongoDB oplog that make change detection in MongoDB much easier than tailing the oplog directly.
Strong support for arrays has always been one of MongoDB's killer features. For example, suppose you have a collection of blog posts where each document contains an array of comments as shown below. Before MongoDB 3.6, you could only update at most one element of the comments array at a time because of limitations with the positional operator $. Array filters in MongoDB 3.6 remove that limitation and add several more exciting features, like updating nested arrays.
One of the major reasons for the mongoose 5 release was the MongoDB driver removing support for the authenticate() function. Up until Mongoose 4.11, that function was the only way mongoose supported doing authentication. In Mongoose 4.11.0, we added the annoying but necessary useMongoClient deprecation warning, and in mongoose 5.0.0-rc0 we deleted 686 lines of legacy connection logic that removed the need for the useMongoClient option. In addition, we made a couple related improvements to the connection API that will make mongoose much cleaner to work with: we made mongoose.connect() always return a promise, and we added a global and connection-level bufferCommands option.
Mongoose 5.0.0-rc0 introduced several important changes to the way middleware works. The most pronounced difference is the ability to use promises and async/await with mongoose middleware. In addition, there are a couple more subtle changes that make the middleware API more consistent. In this article, I'll cover two changes. The first is that post hooks now always get flow control, even synchronous post hooks. The second is that query middleware is applied when the model is compiled for performance reasons.
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Mongoose 5.0.0-rc0 was released yesterday. This is the first backwards-breaking release for mongoose since 4.0.0 was released in March 2015. The major forcing functions for this release were that MongoDB 3.6 removed support for the way mongoose did authentication (which is why mongoose needed the useMongoClient option) and the 3.0.0 release of the official MongoDB Node.js driver. Another major priority for Mongoose 5 was dropping support for Node.js < 4 and MongoDB < 3.0.0. Both Node.js 0.12 and MongoDB 2.6 are about a year past their official end-of-life, and removing support for them has enabled us to make our code base much leaner.
Turf.js has become an indispensible part of my Node.js
Monogram has a powerful middleware system that makes cross-cutting concerns easy. One use case is denormalization, the practice of storing all or part of one document in another document. Denormalization is a powerful paradigm for both performance and data integrity. When done well, denormalization means you only need one query to fetch all necessary data, rather than using joins or $lookup stages that may require their own indexes.
