Distrubute statuses as a fan-out-on-write system, with optional precomputing

app/models/feed.rb

@@ -0,0 +1,27 @@
+class Feed
+  def initialize(type, account)
+    @type    = type
+    @account = account
+  end
+
+  def get(limit, offset = 0)
+    unhydrated = redis.zrevrange(key, offset, limit)
+    status_map = Hash.new
+
+    # If we're after most recent items and none are there, we need to precompute the feed
+    return PrecomputeFeedService.new.(@type, @account).take(limit) if unhydrated.empty? && offset == 0
+
+    Status.where(id: unhydrated).each { |status| status_map[status.id.to_s] = status }
+    return unhydrated.map { |id| status_map[id] }
+  end
+
+  private
+
+  def key
+    "feed:#{@type}:#{@account.id}"
+  end
+
+  def redis
+    $redis
+  end
+end

app/models/status.rb

@@ -67,5 +67,6 @@ class Status < ActiveRecord::Base
 
   after_create do
     self.account.stream_entries.create!(activity: self)
+    FanOutOnWriteService.new.(self)
   end
 end