Add suggestions for enqueuing many jobs and emails

Author: fatkodima

README.adoc

@@ -1956,6 +1956,30 @@ travel_to(Time.current.to_time)
 freeze_time
 ----
 
+== Performance
+
+=== Enqueuing Many Jobs at Once [[enqueuing-many-jobs]]
+
+Prefer enqueuing many jobs and emails at once instead of one by one in a loop.
+This can greatly reduce the number of round-trips to the queue datastore.
+
+[source,ruby]
+----
+# bad
+ids.each { |id| MyJob.perform_later(id) }
+
+# good
+jobs = ids.map { |id| MyJob.new(id) }
+ActiveJob.perform_all_later(jobs)
+
+# bad
+users.each { |user| Notifier.welcome(user).deliver_later }
+
+# good
+emails = users.map { |user| Notifier.welcome(user) }
+ActionMailer.deliver_all_later(emails)
+----
+
 == Managing Processes
 
 === Foreman [[foreman]]