diff --git a/db/docs/ci_runner_namespaces.yml b/db/docs/ci_runner_namespaces.yml
index e6d4693e58ce4d8df0ddc89dd9747727bb58369d..b8450c8e79039a4e8149766da7eabe4c5e5af433 100644
--- a/db/docs/ci_runner_namespaces.yml
+++ b/db/docs/ci_runner_namespaces.yml
@@ -8,3 +8,5 @@ description: Relationships between runners and namespaces for group runners
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/commit/1549239849adf31a078be7503ab2288795e337cf
 milestone: '10.8'
 gitlab_schema: gitlab_ci
+sharding_key:
+  namespace_id: namespaces
diff --git a/spec/lib/gitlab/database/sharding_key_spec.rb b/spec/lib/gitlab/database/sharding_key_spec.rb
index fd5f3db211c29fcd190951d20369eb6cdecd4e48..303f6703f07da74c3c4dec7c8c551b99857074d8 100644
--- a/spec/lib/gitlab/database/sharding_key_spec.rb
+++ b/spec/lib/gitlab/database/sharding_key_spec.rb
@@ -28,6 +28,7 @@
       *['boards.project_id', 'boards.group_id'],
       *['bulk_import_exports.project_id', 'bulk_import_exports.group_id'],
       'ci_pipeline_schedules.project_id',
+      'ci_runner_namespaces.namespace_id',
       'ci_sources_pipelines.project_id',
       'ci_triggers.project_id',
       'gpg_signatures.project_id',