AWS Lambda – comparing platform performances

As Lambda adds nodejs 6.10 to its supported platforms I wondered if there’s any performance differences between the platforms. Thankfully the templates in the Serverless framework make it a relative breeze to test it out with a simple HelloWorld function.

 

The Test

see the test code here.

I created a simple Lambda function for each platform that will respond to an API Gateway event and return “hello”. This is the nodejs version.

I decided to use API Gateway as the trigger as it allows me to invoke the function and apply a constant load using standard load testing tools for HTTP. I chose Artillery because you can get going with minimal fuzz and I had used it before.

For each platform, I ran a test with 10 virtual users sending 1 request per second (ie. a total of 10 req/s) for an hour.

artillery quick —duration 3600 —rate 10 –n 1 http://my.lambda.backed.api/

Since we’re interested in the performance characteristics of the different Lambda platforms, we’ll only be looking at the function Duration metric, and we’ll ignore the initial cold start times.

 

Observation 1 – C# is slower?

Unsurprisingly the invocation duration is fairly consistent across the functions, although C# is sticking out like a sore thumb.

Take this 10 mins window for instance – where there were no spikes that looked like cold starts – the C# platform is consistently higher than the rest.

 

Observation 2 – Java has very consistent performance

If you look at the max duration for the same 10 mins window – for whatever reason, I didn’t get any percentile metrics from CloudWatch for the entire duration of the test so had to settle for max instead – the Java platform was both lower and had less variance, by some distance.

If you compare the average and max duration for the Java platform over a longer time window, you’ll also see that there’s very little difference between the two (if you ignore the spike at 01:38 which might be down to GC pause as opposed to cold start) which suggests the performance of the Java platform is very consistent.

 

Observation 3 – static languages has more consistent performance?

Following on from the previous observation, it seems that both C# and Java shows less variance when it comes to max duration, so perhaps it’s because both are compiled languages?

 

Observation 4 – Java packages are big…

One of the benefits with using nodejs and Python to write Lambda functions is that they produce much smaller packages, which we know translates to lower code start time. Now, the fault might lie with the Serverless template for aws-java-maven, but my HelloWorld Java example produces a whooping 2MB package, which is orders of magnitude bigger than the nodejs and Python functions. I expected it to be bigger than nodejs, but perhaps closer to the size of the C# package.

 

Conclusions

Take these results with a pinch of salt. Things are evolving at an incredible pace and whatever performance discrepancies we’re seeing today can change quickly as AWS improves all the platforms behind the scenes.

Even as I observe that the C# platform appears to be slower in this test, we’re talking about sub-millisecond difference for a HelloWorld example, hardly representative of a real world application. The DotNetCore platform itself (which C# Lambda functions run on) is also evolving quickly, and any future performance improvements in that underlying platform will be transferred to you at no cost, so don’t let this post dissuade you from writing Lambda functions in C#.