Cache project/user combinations.

app/models/user_contributed_projects.rb

@@ -5,9 +5,25 @@ class UserContributedProjects < ActiveRecord::Base
   validates :project, presence: true
   validates :user, presence: true
 
+  CACHE_EXPIRY_TIME = 1.day
+
   def self.track(event)
-    find_or_create_by!(project: event.project, user: event.author)
+    attributes = {project_id: event.project_id, user_id: event.author_id}
+
+    cached_exists?(attributes) do
+      begin
+        find_or_create_by!(attributes)
+        true # not caching the whole record here for now
       rescue ActiveRecord::RecordNotUnique
         retry
       end
+    end
+  end
+
+  private
+
+  def self.cached_exists?(project_id:, user_id:, &block)
+    cache_key = "user_contributed_projects:#{project_id}:#{user_id}"
+    Rails.cache.fetch(cache_key, expires_in: CACHE_EXPIRY_TIME, &block)
+  end
 end

spec/models/user_contributed_projects_spec.rb

@@ -12,16 +12,17 @@ describe UserContributedProjects do
         it 'creates a record' do
           expect { subject }.to change { UserContributedProjects.count }.from(0).to(1)
         end
-
       end
     end
 
     it 'sets project accordingly' do
-      expect(subject.project).to eq(event.project)
+      subject
+      expect(UserContributedProjects.first.project).to eq(event.project)
     end
 
     it 'sets user accordingly' do
-      expect(subject.user).to eq(event.author)
+      subject
+      expect(UserContributedProjects.first.user).to eq(event.author)
     end
 
     it 'only creates a record once per user/project' do