Docker – Mounted volumes for themes being picked up but not served

Hi all, here’s my situation broken down:

I’m using docker/docker-compose to run two containers, one for wordpress (using the official wordpress image) and the other for a mysql database.

In my docker-compose.yml file I’m mounting my local themes folder into the container’s themes folder like so:

wordpress:
  - volumes:
    - ./wp-content/themes:/var/www/html/wp-content/themes

The idea here is that I can run my container to test my site in the environment it will be deployed in, but have fast development using volumes (so I don’t have to constantly rebuild the image–this is for development only).

At this point, what I’m trying to do is a proof-of-concept, so I’m using the ‘nearnothing’ theme for as little complexity as possible.

So I run my container using docker-compose up, and sure enough the volume is being mounted properly. Changes in my local wp-content/themes folder immediately propagate to my container’s /var/www/html/wp-content/themes folder.

The problem, however, is that the changes to the theme are not being served. E.g. I modify my base index.php file to say, “Hello, World!”. I confirm that the container’s theme’s index.php is also updated. To remove the possibility of front-end caching, I use Postman to make a GET request to my site. Sure enough, the change isn’t picked up.

However, after an indiscriminate amount of time (usually anywhere from 10 seconds – 5 minutes), the change is finally served. If I make another change, again I have to wait a certain amount of time before the change is served.

At this point, I thought it might be a plugin. But, the only plugin installed is the akismet spam-catcher plugin. No caching plugins ??

I’m a bit of a newb at WordPress, so is there anything glaringly obvious for why the changes would not be immediately served? Any help is appreciated, thank you.