You might remember locking from your undergrad systems programming class. Locks are what you use when multiple threads want to access the same chunk of memory, and you don't want one thread to clobber the other's data. You don't have threads in Node.js, but that doesn't mean you can ignore concurrency, because your Express server might get conflicting requests at roughly the same time. In this article, I'll describe how you can leverage promises and async functions to enforce the constraint that only one instance of a given function runs at a time.

I often get questions about how to secure user passwords in mongoose. The answer is a one-liner, but I now think there's a better answer: why do you store the user's password in the user document anyway? This may seem blasphemous given that MongoDB's "single view of the customer" use case and that denormalization is one of MongoDB's killer features. However, I've used this paradigm successfully for several projects. In this article, I'll make the case that a separate AuthenticationMethod collection is the way to go for storing password hashes in your database.

Express' error handling middleware is a powerful tool for consolidating your HTTP error response logic. Odds are, if you've written Express code you've written code that looks like what you see below.

In 2015, I started working on a new ODM for MongoDB and Node.js. It was based on the now-obsolete Object.observe() function, and I unfortunately had to scrap the whole project when the Object.observe() proposal was unexpectedly withdrawn. A lot of the core logic from the original ODM lives on in Archetype. But my brief time in Redux land and studying falcor taught me a crucial lesson: the Model-View-Controller paradigm is not the only way to do things. MVC and ODMs still make sense, but we can build a stronger, more functional abstraction as the basis for a more concise architecture. The new monogram has now been powering 100% of Booster's API queries for weeks and it's officially production ready. Here's what monogram is all about.

Mongoose 4.11 introduced an important new option to work around a major deprecation. The useMongoClient option is the source of the 'open() is deprecated in mongoose' deprecation warning that has caused so much discussion. This option opts you in to using Mongoose 4.11's simplified initial connection logic and allows you to avoid getting a deprecation warning from the underyling MongoDB driver.

Mongoose 4.11 was released last week and includes several neat new features. It also has one very important deprecation, so before you upgrade please read about the useMongoClient option in the docs. I'll write more about useMongoClient and why it is necessary another time. But first, mongoose 4.11 enables a new plugin, mongoose-lean-virtuals, which lets you apply virtuals to query results even if you use the lean() function. This plugin is a more general version of mongoose-lean-id.

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.