diff --git a/Gemfile b/Gemfile
index d2d6db9..d2167cd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,6 +7,7 @@ gem "byebug"
 
 gem "sqlite3"
 gem "httparty"
+gem "concurrent-ruby"
 
 gem "aws-sdk", "~> 2", require: false
 gem "google-cloud-storage", "~> 1.3", require: false
diff --git a/Gemfile.lock b/Gemfile.lock
index cce1d34..aa8d175 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -10,29 +10,29 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    actionpack (5.1.1)
-      actionview (= 5.1.1)
-      activesupport (= 5.1.1)
+    actionpack (5.1.2)
+      actionview (= 5.1.2)
+      activesupport (= 5.1.2)
       rack (~> 2.0)
       rack-test (~> 0.6.3)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.2)
-    actionview (5.1.1)
-      activesupport (= 5.1.1)
+    actionview (5.1.2)
+      activesupport (= 5.1.2)
       builder (~> 3.1)
       erubi (~> 1.4)
       rails-dom-testing (~> 2.0)
       rails-html-sanitizer (~> 1.0, >= 1.0.3)
-    activejob (5.1.1)
-      activesupport (= 5.1.1)
+    activejob (5.1.2)
+      activesupport (= 5.1.2)
       globalid (>= 0.3.6)
-    activemodel (5.1.1)
-      activesupport (= 5.1.1)
-    activerecord (5.1.1)
-      activemodel (= 5.1.1)
-      activesupport (= 5.1.1)
+    activemodel (5.1.2)
+      activesupport (= 5.1.2)
+    activerecord (5.1.2)
+      activemodel (= 5.1.2)
+      activesupport (= 5.1.2)
       arel (~> 8.0)
-    activesupport (5.1.1)
+    activesupport (5.1.2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (~> 0.7)
       minitest (~> 5.1)
@@ -41,26 +41,26 @@ GEM
       public_suffix (~> 2.0, >= 2.0.2)
     arel (8.0.0)
     ast (2.3.0)
-    aws-sdk (2.10.7)
-      aws-sdk-resources (= 2.10.7)
-    aws-sdk-core (2.10.7)
+    aws-sdk (2.10.11)
+      aws-sdk-resources (= 2.10.11)
+    aws-sdk-core (2.10.11)
       aws-sigv4 (~> 1.0)
       jmespath (~> 1.0)
-    aws-sdk-resources (2.10.7)
-      aws-sdk-core (= 2.10.7)
-    aws-sigv4 (1.0.0)
+    aws-sdk-resources (2.10.11)
+      aws-sdk-core (= 2.10.11)
+    aws-sigv4 (1.0.1)
     builder (3.2.3)
     byebug (9.0.6)
     concurrent-ruby (1.0.5)
     declarative (0.0.9)
     declarative-option (0.1.0)
     digest-crc (0.4.1)
-    erubi (1.6.0)
+    erubi (1.6.1)
     faraday (0.12.1)
       multipart-post (>= 1.2, < 3)
     globalid (0.4.0)
       activesupport (>= 4.2.0)
-    google-api-client (0.13.0)
+    google-api-client (0.13.1)
       addressable (~> 2.5, >= 2.5.1)
       googleauth (~> 0.5)
       httpclient (>= 2.8.1, < 3.0)
@@ -87,7 +87,7 @@ GEM
     httparty (0.15.5)
       multi_xml (>= 0.5.2)
     httpclient (2.8.3)
-    i18n (0.8.4)
+    i18n (0.8.6)
     jmespath (1.3.1)
     jwt (1.5.6)
     little-plugger (1.1.4)
@@ -100,13 +100,13 @@ GEM
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
-    mini_portile2 (2.1.0)
+    mini_portile2 (2.2.0)
     minitest (5.10.2)
     multi_json (1.12.1)
     multi_xml (0.6.0)
     multipart-post (2.0.0)
-    nokogiri (1.7.2)
-      mini_portile2 (~> 2.1.0)
+    nokogiri (1.8.0)
+      mini_portile2 (~> 2.2.0)
     os (0.9.6)
     parallel (1.11.2)
     parser (2.4.0.0)
@@ -157,6 +157,7 @@ DEPENDENCIES
   aws-sdk (~> 2)
   bundler (~> 1.15)
   byebug
+  concurrent-ruby
   google-cloud-storage (~> 1.3)
   httparty
   rake
diff --git a/lib/active_storage/async_uploader.rb b/lib/active_storage/async_uploader.rb
new file mode 100644
index 0000000..dd448a3
--- /dev/null
+++ b/lib/active_storage/async_uploader.rb
@@ -0,0 +1,34 @@
+require "concurrent/promise"
+
+class ActiveStorage::AsyncUploader
+  class << self
+    def result(uploaders)
+      promises = uploaders.map(&:promise)
+      Concurrent::Promise.zip(*promises).value!
+    end
+  end
+
+  attr_reader :promise
+
+  def initialize(service, key, checksum: nil)
+    @data = ""
+    @eof = false
+    @promise = Concurrent::Promise.execute do
+      until eof? do; end
+      service.upload key, StringIO.new(@data), checksum: checksum
+    end
+  end
+
+  def eof?
+    @eof
+  end
+
+  def write(chunk)
+    @data << chunk
+    @eof = false
+  end
+
+  def close
+    @eof = true
+  end
+end
diff --git a/lib/active_storage/service/mirror_service.rb b/lib/active_storage/service/mirror_service.rb
index 54465ca..d06f308 100644
--- a/lib/active_storage/service/mirror_service.rb
+++ b/lib/active_storage/service/mirror_service.rb
@@ -1,6 +1,9 @@
 require "active_support/core_ext/module/delegation"
+require "active_storage/async_uploader"
+require "concurrent/promise"
 
 class ActiveStorage::Service::MirrorService < ActiveStorage::Service
+  CHUNK_SIZE = 1024
   attr_reader :primary, :mirrors
 
   delegate :download, :exist?, :url, to: :primary
@@ -17,13 +20,18 @@ def initialize(primary:, mirrors:)
   end
 
   def upload(key, io, checksum: nil)
-    each_service.collect do |service|
-      service.upload key, io.tap(&:rewind), checksum: checksum
+    uploaders = each_service.collect do |service|
+      ActiveStorage::AsyncUploader.new(service, key, checksum: checksum)
     end
+    io.rewind
+    while chunk = io.read(CHUNK_SIZE)
+      uploaders.each { |uploader| uploader.write(chunk) }
+    end
+    ActiveStorage::AsyncUploader.result(uploaders.each(&:close))
   end
 
   def delete(key)
-    perform_across_services :delete, key
+    perform_async_across_services :delete, key
   end
 
   private
@@ -31,10 +39,10 @@ def each_service(&block)
       [ primary, *mirrors ].each(&block)
     end
 
-    def perform_across_services(method, *args)
-      # FIXME: Convert to be threaded
-      each_service.collect do |service|
-        service.public_send method, *args
+    def perform_async_across_services(method, *args)
+      promises = each_service.collect do |service|
+        Concurrent::Promise.execute { service.public_send method, *args }
       end
+      Concurrent::Promise.zip(*promises).value!
     end
 end