```ruby
class CreateHeartbeats < ActiveRecord::Migration
  def change
    create_table :heartbeats do |t|
      t.integer :device_id
      t.integer :reporting_device_id

      t.timestamps null: false
    end
  end
end
```

Remove updated_at column from heartbeats table
user
```ruby
class CreateHeartbeats < ActiveRecord::Migration
  def change
    create_table :heartbeats do |t|
      t.integer :device_id
      t.integer :reporting_device_id
      t.datetime :created_at, nil: false
    end
  end
end
```
assistant