perf: load widget request context in fewer queries

Every widget request loaded the web widget, its inbox, the account, the contact inbox and the contact with one query each. The widget endpoints run about 230M times a week in production, and widget/contacts#show runs these five queries and nothing else.

The web widget, inbox and account now come from one joined query, and the contact inbox and contact from another.

The inbox members view also called find_by on account_users for each member, which queries every time. Production averaged 8.5 of those per request. The controller now preloads account_users and the view picks the row in Ruby.

A replay of one average production minute of widget GET traffic, 21,138 requests, went from 141,129 queries to 67,995 locally, with identical responses.

app/controllers/api/v1/widget/inbox_members_controller.rb

@@ -2,6 +2,6 @@ class Api::V1::Widget::InboxMembersController < Api::V1::Widget::BaseController
   skip_before_action :set_contact
 
   def index
-    @inbox_members = @web_widget.inbox.inbox_members.includes(user: { avatar_attachment: :blob })
+    @inbox_members = @web_widget.inbox.inbox_members.includes(user: [:account_users, { avatar_attachment: :blob }])
   end
 end

app/controllers/concerns/website_token_helper.rb

@@ -4,14 +4,14 @@ module WebsiteTokenHelper
   end
 
   def set_web_widget
-    @web_widget = ::Channel::WebWidget.find_by!(website_token: permitted_params[:website_token])
+    @web_widget = ::Channel::WebWidget.eager_load(inbox: :account).find_by!(website_token: permitted_params[:website_token])
     @current_account = @web_widget.inbox.account
 
     render json: { error: 'Account is suspended' }, status: :unauthorized unless @current_account.active?
   end
 
   def set_contact
-    @contact_inbox = @web_widget.inbox.contact_inboxes.find_by(
+    @contact_inbox = @web_widget.inbox.contact_inboxes.eager_load(:contact).find_by(
       source_id: auth_token_params[:source_id]
     )
     @contact = @contact_inbox&.contact

app/views/api/v1/widget/inbox_members/index.json.jbuilder

@@ -5,6 +5,8 @@ json.payload do
     json.id inbox_member.user.id
     json.name inbox_member.user.available_name
     json.avatar_url inbox_member.user.avatar_url
-    json.availability_status inbox_member.user.account_users.find_by(account_id: @current_account.id)&.availability_status
+    # account_users is preloaded; find_by would query once per member
+    account_user = inbox_member.user.account_users.find { |record| record.account_id == @current_account.id }
+    json.availability_status account_user&.availability_status
   end
 end