Every company I've worked at had similar (though far less costly) issues. Put an API method in every service that exposes the SHA of the running code, the buil

Every company I've worked at had similar (though far less costly) issues. Put an API method in every service that exposes the SHA of the running code, the build time of the binary (if compiled), and the timestamp when the deploy was initiated. (btw, having this information in the filesystem is insufficient, because what if a post-deploy restart failed?) Verify after every deploy.