Switch to memory_store for caching in production [SCI-3182]

config/environments/development.rb

@@ -118,7 +118,7 @@ Rails.application.configure do
   if Rails.root.join('tmp/caching-dev.txt').exist?
     config.action_controller.perform_caching = true
 
-    config.cache_store = :memory_store
+    config.cache_store = :memory_store, { size: (ENV['RAILS_MEM_CACHE_SIZE_MB'] || 32).to_i.megabytes }
     config.public_file_server.headers = {
       'Cache-Control' => "public, max-age=#{2.days.seconds.to_i}"
     }

config/environments/production.rb

@@ -78,9 +78,6 @@ Rails.application.configure do
   # Use a different logger for distributed setups.
   # config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)
 
-  # Use a different cache store in production.
-  # config.cache_store = :mem_cache_store
-
   # Enable serving of images, stylesheets, and JavaScripts from an asset server.
   # config.action_controller.asset_host = 'http://assets.example.com'
 
@@ -129,7 +126,7 @@ Rails.application.configure do
   end
 
   # Use a different cache store in production.
-  # config.cache_store = :mem_cache_store
+  config.cache_store = :memory_store, { size: (ENV['RAILS_MEM_CACHE_SIZE_MB'] || 32).to_i.megabytes }
 
   # Use a real queuing backend for Active Job (and separate queues per environment)
   config.active_job.queue_adapter     = :delayed_job