backendBinary backend implements HTTP server that handles task queues and crons.
frontendBinary frontend implements HTTP server that handles requests to 'default' module.
implPackage impl instantiates the full implementation of the CIPD backend services.
impl/adminPackage admin contains implementation of cipd.Admin RPC service.
impl/casPackage cas contains implementation of cipd.Storage service RPC service.
impl/cas/tasksPackage tasks contains task queue tasks definitions.
impl/gsPackage gs implement Google Storage API wrapper used by CIPD backend.
impl/metadataPackage metadata implements handling of prefix metadata.
impl/modelPackage model contains core CIPD datastore entities.
impl/monitoringPackage monitoring implements monitoring used by CIPD backend.
impl/repoPackage repo contains implementation of cipd.Repository service RPC service.
impl/repo/processingPackage processing contains code related to post-registration instance processing.
impl/repo/tasksPackage tasks contains task queue tasks definitions.
impl/rpcaclPackage rpcacl contains helpers for checking ACLs of individual RPCs.
impl/testutilPackage testutil contains helpers used from CIPD backend unit tests.
uiPackage ui implements request handlers that serve user facing HTML pages.

Updated 2020-11-26. Refresh now. Tools for package owners.