Just found an interesting issue that manifested itself in production but wasn't caught in development and testing.
We have a config file in app/Config/AWS.php that is working on the local development machine (running PHP in a docker container, mounting the macOS directory). The code refers to this configuration file as $config = config('Aws'); and all works locally when developing and testing.
After preparing the Docker for the production system - this particular piece of code fails, returning null and generating a 500 error.
Huh?
Turns out the mounting of the macOS file-system in Docker is in fact case-insensitive even though the Docker image running php and apache is a Linux system which is case-sensitive. In the local development Docker, the following commands all work:
more app/Config/aws.php
more app/Config/AWS.php
more app/Config/Aws.php
Running in the production Docker the issue is that the argument to config() is Aws so the framework tries to locate the file named app/Config/Aws.php but fails!
Lesson learned.