usar un controlador de api

app/controllers/api_controller.rb

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+class ApiController < ActionController::API
+  # Por ahora hacer un echo de cada transacción
+  #
+  # @see {https://docutopia.tupale.co/sutty:nodemecu:api}
+  def transactions
+    render plain: params[:transaction_uuid], status: :ok
+  end
+end

app/controllers/application_controller.rb

@@ -7,11 +7,4 @@ class ApplicationController < ActionController::Base
   end
   def index
   end
-
-  # Por ahora hacer un echo de cada transacción
-  #
-  # @see {https://docutopia.tupale.co/sutty:nodemecu:api}
-  def transactions
-    render plain: params[:transaction_uuid], status: :ok
-  end
 end

config/routes.rb

@@ -6,5 +6,5 @@ Rails.application.routes.draw do
   end
   mount Blazer::Engine, at: 'blazer'
 
-  post :transactions, to: 'application#transactions'
+  post :transactions, to: 'api#transactions'
 end