Deploying a Flask 2.x App Using Zappa

Ryan Sandridge · August 18, 2021

I write application code, and my undestanding of cloud infrastructure is only barely better than my understanding of frontend development. While I’m always growing that cloud knowledge, I don’t want to spend a lot of time fiddling with it just to get a weekend personal project deployed. So I was drawn to Zappa.

I use AWS in my day job, so I wanted to use it for my side project too. So I wanted a tool that would deploy a small Flask app to AWS Lambda that would handle all the boring details. I considered just developing a Chalice app instead of Flask, but I didn’t want to use a framework for the app that is developed with a single cloud vender in mind. You may be saying, “but Ryan, Zappa only targets AWS”, and you’d be right, but I’m still writing just a plain old Flask app that can be deployed in any number of ways to any number of vendors if/when I so choose.

But when I tried to follow the very simple steps as advertised on the side of the tin:

$ pip install zappa
$ zappa init
$ zappa deploy

I was met with a very frustrating error simply upon pip installing zappa:

ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
flask 2.0.1 requires Werkzeug>=2.0, but you have werkzeug 0.16.1 which is incompatible.

Oh dear, what to do? There are open issue’s on the Zappa Github Repo dating back to February 2020 😱. I don’t know what’s going on with Zappa, and this issue neglect is a pretty big red flag, but the alternatives (Architect, serverless, etc.) are appear to be more complex than I wanted for a weekend side project.

But in the Github Issues, there was enough information on how to circumnavigate this problem that I turned a blind eye to the warning signs, and moved forward with Zappa. Here is how I did it.

  • I forked Zappa and made these changes (which also adds support for Python 3.9.x)
  • Then I pip installed directly from my fork like this:
    python -m pip install git+

And thats it (unless I forgot something)! Now I’m deploying my tiny Flask app to AWS Lambda.

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