Abbreviated example code that was exhibiting an N+1 only for non-image (video/pdf) preview representations

feeds_controller.rb

class FeedsController < ApplicationController
  def index
    @posts = Post.with_visuals.order(published_at: :desc)
  end
end

index.html.erb

<div class="flex">
  <% @posts.each do |post| %>
    <%= link_to feed_post_path(post, post.web_path) do %>
      <%= image_tag "https://#{ENV["CDN_HOST"]}/#{post.preview_image.key}" %>
    <% end %>
  <% end %>
</div>

post.rb

class Post < ApplicationRecord
  belongs_to :user
  has_many :visuals, -> { order(position: :asc) }, dependent: :destroy

  accepts_nested_attributes_for :visuals, allow_destroy: true, limit: 10

  def self.with_visuals
    includes(:visuals).merge(Visual.with_attached_file)
  end

  def preview_image
    visuals.first.file.representation(:preview)
  end
end

visual.rb

class Visual < ApplicationRecord
  belongs_to :post

  has_one_attached :file, dependent: :purge_later do |attachable|
    attachable.variant :preview, resize_to_fill: [200, 200], preprocessed: true
  end
end