Calculate the checksum for outdated projects with less activity first

ee/app/finders/geo/repository_verification_finder.rb

@@ -5,6 +5,7 @@ module Geo
        .with_route
        .joins(:repository_state)
        .where(repository_outdated.or(wiki_outdated))
+       .order(last_repository_updated_at_asc)
        .limit(batch_size)
     end
 
@@ -62,5 +63,9 @@ module Geo
     def repository_never_verified
       repository_state_table[:project_id].eq(nil)
     end
+
+    def last_repository_updated_at_asc
+      Gitlab::Database.nulls_last_order('projects.last_repository_updated_at', 'ASC')
+    end
   end
 end

ee/spec/finders/geo/repository_verification_finder_spec.rb

@@ -43,6 +43,16 @@ describe Geo::RepositoryVerificationFinder, :postgresql do
 
       expect(subject.find_outdated_projects(batch_size: 10)).to be_empty
     end
+
+    it 'returns less active projects first' do
+      less_active_project = create(:project)
+      create(:repository_state, :repository_outdated, project: project)
+      create(:repository_state, :repository_outdated, project: less_active_project)
+      project.update_column(:last_repository_updated_at, 30.minutes.ago)
+      less_active_project.update_column(:last_repository_updated_at, 2.days.ago)
+
+      expect(subject.find_outdated_projects(batch_size: 10)).to eq [less_active_project, project]
+    end
   end
 
   describe '#find_unverified_projects' do