The official chia container in docker-hub is a hefty 238MB, but many people running chia-blockchain in Docker just want a relatively light, tiny installation for farming.
Note! There is an effort to create around a 200MB docker image in this pull request, but it’s not complete yet.
With a few tweaks, I was able to mine down to around 111MB, shaving off around half of the final compressed size.
I don’t recommend you use my image directly, as it’s a hobby effort.