Build cache isn't guaranteed on Railway because the build system scales elastically, so your build may land on a node without your previous cache. When cache is missed and your requirements.txt changes, the full dependency tree must be reinstalled. Your services are pulling heavy AI packages which are inherently slow to download and install - this is the source of the hour-long builds. To get consistent fast builds, you'll need to build your own Docker images externally and deploy them directly, or optimize your dependencies.