Monday, September 4, 2017

Amazon Lightsail network rate limited?

Amazon Lightsail is the entry-level hosted server platform provided by Amazon AWS. For $5 per month, you get a bundle including the server, storage, network, and DNS hosting for one zone. You could assemble something similar using Amazon EC2 services, but the result would cost a little more and some costs such as network bandwidth would be unpredictable because they'd be billed based on usage. In putting together the Lightsail packages, it's pretty clear that Amazon is deliberately intending to compete head-to-head with the standard Droplets from DigitalOcean.

It's "common knowledge" that the Lightsail servers are packaged versions of the EC2 t2-series servers. In this model, the $5 Lightsail server based on, and expected to provide the performance of, a t2.nano server. However, in using a bottom-tier Lightsail server for a small project, this has not been my experience. It feels like compromise have been introduced by Amazon to try and compete on cost with DigitalOcean but not cannibalize sales of fully-featured entry level AWS instances.

By design, the t2 servers are subject to CPU resource throttling based on recent usage. However, they have no issue serving multiple Megabytes per second to the network. Unfortunately this has not been my experience with the Lightsail servers. In fact, using a $5 Lightsail server, I've consistently observed outbound network throughput limited to 64 KiB/second. I've done transfers at different times of day, through http, https, and scp, and never significantly exceeded 64 KiB/second. In fact, when copying a file a few MiB in size, observed data transfer rate is a little less than 64 KiB/second because of protocol overheads.

For a cheap server, this seems like it shouldn't be a big deal - after all, you're not paying for a whole lot. However, modern web frameworks end up causing a simple page to require several hundred KiB of data to render properly, due to embedded javascript libraries, web fonts, and so on. The result is a simple Wordpress landing page without any images being accessed by one user takes 3 seconds just to load because of network rate limiting. With search engines factoring page load time in their ranking algorithms, this makes a Lightsail-hosted prototype site unlikely to do well in search rankings regardless of whatever other SEO tricks you use.

Amazon could mitigate this to some extent by making whatever rate limiting they've implemented "burstable", i.e. for the first few seconds a connection can transfer data quickly before being slowed down to ensure you don't exceed your allowance. This would make these servers much more responsive for light web serving duties. For whatever reason they seem to have chosen to use a flat rate cap instead.

If you've decided to use Amazon to host your prototype site on small servers and are considering using Lightsail, think carefully. Unless you really need the guarantee of fixed cost, the EC2 t2 series servers are likely to offer a better user experience because of much higher outbound bandwidth available, and therefore potentially better page rankings, for not much more cost.

Amazon has a free guide to managing Linux on EC2 available here.

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