[irjustin]

While you missed the point of the saturation comment, this is why we love AWS Lambda over ECS+Fargate.

Rails has really poor startup time due to loading all codepaths. We switched to Django and it runs beautifuly on AWS Lambda where our CI is more expensive than actual server costs. We're a b2b application so traffic is quite low so we REALLY don't saturate the CPU in a normal Fargate setup.

[cocoflunchy]

I'm surprised to see a mention of Django when talking about fast startup times! This is one of my main issues with Django at the moment. How big is your project?

Our ~500k lines app takes multiple seconds to start, which is why I'm not really investigating a lambda-style setup... Do you have specific strategies to make startup fast?

[irjustin]

Apologies on the lay reply.

Your app is significantly bigger than ours, so grain of salt.

We play very close attention to what's loaded on startup. There are two key tricks.

1. Heavy libraries/packages load at runtime and are only in the "background job" codepath.

  def my_heavy_func():
    from heavy_library import sum_heavy_function
    
    sum_heavy_function()

vs the import at top of file.

2. Limit which apps are loaded via `INSTALLED_APPS`, again no heavy packages.

Lambda is SUPER nice for us. The bottleneck becomes the DB. Webserver can basically never go down on its own as you can create 1000x by default.

Best of Luck!