On the other side, you get config-as-code if you do bundle it with the docker image…
Gotcha. You could opt to store in an external store like DynamoDB or Workers KV. Fly does have a KV store in Fly-managed Uptash Redis, and your usecase may be covered by its free tier. Lastly, it isn’t a KV store, but another Fly-specific alternative would be deploy (and maintain) LifeFS (docs).
Experimental Consul support is also available to Fly apps that one may (ab)use to store configs… (though I haven’t see any one recommend it on here).