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Danielle Heberling for AWS Community Builders

Posted on • Originally published at on

The Problem with "It Works on My Computer"

Disclaimer: This is an opinionated post based off of my own experience. Your experience and opinions may differ and that is okay. I welcome your respectful and engaged conversation. Most of my cloud experience is with Amazon Web Services, so this post will be AWS heavy. A lot of this applicable to other cloud providers though.

Scenario #1: Working on a serverless first team

We hire a new person that’s new to serverless. Regardless of how long they’ve been a professional software developer, the first question is often some variation of:

“How do I run this locally on my computer?”

There are many tools out there that can emulate AWS on your computer, but I’ve experienced some issues with this approach.

  • The tools are not always accurate or up to date with the latest features available in the cloud.
  • The environment on your computer vs in the cloud will be different. Some common examples include: environment variables, database connections, and permissions to access resources.
  • Maintaining the tooling required to emulate can sometimes be more work than deploying your changes and testing in the cloud. A lot of them require knowledge of Docker and Docker networking. My biased opinion: at that point why go serverless in the first place?

Scenario #2: Working on a non-serverless first team

Some companies use more traditional infrastructure such as EC2 instances and RDS. Running a local version of a Node.js server against a local Postgres database is great for fast, iterative development and works well most of the time.

Where this falls apart is when integrating another AWS service such as S3. I’ve seen software developers who do not have much cloud experience, but are great at writing code do the following:

  • Authenticate with AWS using administrative access credentials locally on their computer.
  • Run a server locally on their computer which uploads a file to an S3 bucket located in a non-prod AWS account.
  • It works!
  • They submit their code and it gets merged into the main branch.
  • The code gets deployed to a non-prod environment (staging or something similar).
  • They test uploading to the S3 bucket and it fails on the non-prod environment.
  • “I don’t know what’s going on because it worked locally for me!” 🤔

Man looking confused>

Photo by Sander Sammy on Unsplash

  • Someone more experienced with IAM recognizes that the permissions on the cloud and the local environment differ.
  • The more experienced person fixes the permissions issues in the cloud. 🚀

Unsolicited advice

  • Have a non-prod cloud environment where you can test code changes before deploying to prod. It’s good to catch problems before your end users do. ❤️
  • If you’re running servers locally as part of your development loop, authenticate locally using similar permissions that the production server uses. This will help catch permissions issues sooner. 🤓
  • If you’re working on a serverless first team, do not attempt to run your application locally. Instead, deploy your code to a sandbox account and test it there. One AWS account per developer. It’s also a great way to get more familiar with troubleshooting in the cloud. 🙌🏻


I’ve seen these scenarios play out on many different teams at different companies. The reason is due to developers needing to change their mindset.

Today it is very common for software applications to use cloud services. We as developers should also evolve our development environments to match the new paradigm.

Let’s build better software together. Good luck out there. 💪🏻

Top comments (1)

segdeha profile image
Andrew Hedges

"It works on my machine…"

"So, let's ship your machine."

And that's how Docker was born 😂