Redis caching for expensive computations

                  class TrendingPostsService
  CACHE_KEY = 'trending_posts:v1'.freeze
  CACHE_TTL = 15.minutes

  def self.call(limit: 10)
    Rails.cache.fetch(CACHE_KEY, expires_in: CACHE_TTL) do
      compute_trending_posts(limit)
    end
  end

  def self.compute_trending_posts(limit)
    # Expensive calculation combining views, likes, recency
    Post.published
        .where('created_at >= ?', 7.days.ago)
        .select('posts.*,
                (LOG(posts.views + 1) * 0.5 +
                 LOG(posts.likes_count + 1) * 0.3 +
                 (EXTRACT(EPOCH FROM posts.created_at) / 100000) * 0.2) AS trending_score')
        .order('trending_score DESC')
        .limit(limit)
        .to_a
  end

  def self.clear_cache
    Rails.cache.delete(CACHE_KEY)
  end
end