You might remember locking from your undergrad systems programming class. Locks help when multiple threads that can be interrupted at any time access a shared resource. In distributed programming (like building a Node.js server that talks to a database) you have a similar problem: parallel operations can mutate documents in the database in conflicting ways. In particular, enforcing uniqueness, such as making sure only one user has a given email, is tricky.

Mongoose setters have always had the limitation that they only work for save(), not for queries. For example, let's say you have a schema that enforces your emails are always lowercase:

One great perk of async/await in Node.js is how well it integrates with existing libraries. By now, most popular Node.js libraries support some sort of promise-based API, so they integrate nicely with async/await. You might even have the pleasure of removing a few dependencies from your package.json if you start using async/await instead of co. In this article, I'll show you how async/await works with mocha tests, express routes and middleware, and mongoose queries and cursors.

Mongoose 4.10.0 just landed and brings with it several powerful features and bug fixes. The most +1-ed feature in this supporting unique in array definitions via the mongoose-unique-array plugin. This feature is implemented as a separate plugin because mongoose-unique-array does much more than simply create a unique index, it also ties in to validators and versioning. In this article, I'll explain how to use mongoose-unique-array and the caveats you need to be aware of when using it.

I've been looking at PubNub as a potential alternative to Firebase for push notifications. At a high level, PubNub is pubsub-as-a-service: once you plug in PubNub's JavaScript library, you can start publishing messages and subscribing to channels without having to deploy Kafka, ZeroMQ, etc.

pkg is Zeit's (the company behind Next.js) new tool for bundling Node.js projects into standalone binary executables. A standalone executable has numerous advantages: as long as you're on a compatible OS, you can run the executable without installing Node.js, docker, or any other runtime. You can ship your executable to a vanilla EC2 instance and run it without any extra setup, no need to maintain AMIs or use Packer. You can also cross-compile with pkg, so you can build an OSX-compatible executable on your Linux box and vice-versa. In other words, pkg gives you the best parts of Golang in Node.js.

Next.js is a powerful framework for building server-side rendered applications. Next.js is just a wrapper around React, but it abstracts away all the ugly bits of React: build systems, transpilation, routing, CSS, etc. Most importantly, it makes server-side rendering with React dead simple, no need to carefully structure your code for use with preact-render-to-string or figure out the lastChild pattern for replacing the server-side rendered component with the client-side rendered component. In this article, I'll show you how to build a basic Next.js app with server-side rendering on top of an Express and MongoDB API.