RavenDB Cloud has a whole bunch of new features that were quietly launched in the past few months. I talked about them in this post. It turns out that the team keeps on delivering new stuff, faster than I can write about it.

The new feature is a really interesting one, because it is pretty simple to understand and has some interesting implications for production.

You need to explicitly enable auto-scaling on your cluster, this is how this looks like:

Once you enabled auto-scaling - which usually takes under a minute, you can click on the Configure button to set your own policies:

Here is what this looks like:

The idea is very simple, we routinely measure the load on the system, and if we detect a high CPU threshold for a long time, we’ll kick off scaling to the next tier (or maybe higher, see the Upscaling / Downscaling step options) to provide additional resources to the system. If there isn’t enough load (as measured in CPU usage), we will downscale back to the lowest instance type.

Conceptually, this is a pretty simple setup. You use a lot of CPU - you get a bigger machine that has more resources to use, until it all balances out.

Now, let’s talk about the implications of this feature. To start with, it means that you only pay based on your actual load, and you don’t need to over-provision to match peak load.

The design of this feature and RavenDB in general means that we’ll be able to make scale up and scale down changes without any interruption in service. That means that you can let the auto-scaling manage the size of your instances.

In the image above, you may have noticed that I’m using the PB line of products (PB10 … PB50). That stands for burstable instances, which consume CPU credits if they are in use. How that plays with auto-scaling is really interesting.

As you use more CPU, you consume all the CPU credits, and your CPU usage is high. At this point, the auto-scaling kicks in and moves you to a higher tier. That gives you both more baseline CPU credits and higher CPU credits accrual rate.

Together with zero downtime upscaling and downscaling, it means that you can benefit from the burstable instances' lower cost without having to worry about running out of resources.

Note that auto-scaling only applies to the same family of instances. So if you are running on burstable instances, you’ll get scaling from burstable instances, and if you are running on the P series (non burstable) your auto-scaling will use P instances.

Note that we offer auto scaling for development instances as well. There, however, there is just a single RavenDB instance, so auto-scaling will trigger, but you’ll have up to two minutes in which we scale the instance and it will be inaccessible.  That isn’t an issue for the production tier.