Replaced constant PO_RATES with a cached model key

app/lib/economy/cost_with_po_rate.rb

@@ -2,9 +2,6 @@ module Economy
   # Calulates costs of type FamilyAndEmergencyHomeCost and ExtraContribution
   #   that requires PoRate for a contractor
   class CostWithPoRate < Base
-
-    PO_RATES = PoRate.all.to_a.freeze
-
     def initialize(cost, options = {})
       @cost = cost
       @interval = { from: (options[:from] || cost.period_start), to: (options[:to] || Date.today) }
@@ -72,7 +69,7 @@ def months_and_po_rates(interval)
     end
 
     def po_rate_for_date(date)
-      po_rate = PO_RATES.find do |rate|
+      po_rate = PoRate.all_cached.find do |rate|
         rate.start_date <= date && rate.end_date >= date
       end
 

app/models/po_rate.rb

@@ -8,4 +8,12 @@ class PoRate < ApplicationRecord
   validate do
     date_range(:start_date, start_date, end_date)
   end
+
+  after_commit do
+    Rails.cache.delete('PoRate/all')
+  end
+
+  def self.all_cached
+    Rails.cache.fetch('PoRate/all') { all.load }
+  end
 end