Agreed, we might not have done it if we had to resort to having the application download its own dependencies at startup. In our case, our Mesos scheduler, Sing

Agreed, we might not have done it if we had to resort to having the application download its own dependencies at startup. In our case, our Mesos scheduler, Singularity, handles S3 artifacts at deploy time for us. Previously we gave it a single S3 URL for the fat JAR, but now we just give it a list of artifacts (the app plus its dependencies) and it handles everything for us so it's not much more complexity and ended up being really easy to integrate into our deploy process. By the time the app starts up, all of its dependencies are guaranteed to be present (if an S3 download failed, the deploy would have failed) so it's totally transparent to the application.