feat: configure auto db switching

config/environments/production.rb

@@ -102,5 +102,28 @@ Rails.application.configure do
   # :sendgrid for Sendgrid
   config.action_mailbox.ingress = ENV.fetch('RAILS_INBOUND_EMAIL_SERVICE', 'relay').to_sym
 
+  # Enable Database Selector
+  #
+  # Inserts middleware to perform automatic connection switching.
+  # The `database_selector` hash is used to pass options to the DatabaseSelector
+  # middleware. The `delay` is used to determine how long to wait after a write
+  # to send a subsequent read to the primary.
+  #
+  # The `database_resolver` class is used by the middleware to determine which
+  # database is appropriate to use based on the time delay.
+  #
+  # The `database_resolver_context` class is used by the middleware to set
+  # timestamps for the last write to the primary. The resolver uses the context
+  # class timestamps to determine how long to wait before reading from the
+  # replica.
+  #
+  # By default Rails will store a last write timestamp in the session. The
+  # DatabaseSelector middleware is designed as such you can define your own
+  # strategy for connection switching and pass that into the middleware through
+  # these configuration options.
+  config.active_record.database_selector = { delay: 2.seconds }
+  config.active_record.database_resolver = ActiveRecord::Middleware::DatabaseSelector::Resolver
+  config.active_record.database_resolver_context = ActiveRecord::Middleware::DatabaseSelector::Resolver::Session
+
   Rails.application.routes.default_url_options = { host: ENV['FRONTEND_URL'] }
 end