diff --git a/Gemfile.lock b/Gemfile.lock
index cfa2824..bd3055a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -3,6 +3,7 @@ PATH
   specs:
     appsignal-sourcemap (1.0.0.develop)
       appsignal (~> 3.0)
+      parallel (~> 1.0)
 
 GEM
   remote: https://rubygems.org/
diff --git a/appsignal-sourcemap.gemspec b/appsignal-sourcemap.gemspec
index 583412f..67f2e6e 100644
--- a/appsignal-sourcemap.gemspec
+++ b/appsignal-sourcemap.gemspec
@@ -21,6 +21,7 @@ Gem::Specification.new do |spec|
   spec.files = Dir["lib/**/*", "README.md"]
 
   spec.add_dependency "appsignal", "~> 3.0"
+  spec.add_dependency "parallel", "~> 1.0"
 
   spec.add_development_dependency "standard"
 end
diff --git a/lib/appsignal/sourcemap/supervisor.rb b/lib/appsignal/sourcemap/supervisor.rb
index 49549ae..f9330e5 100644
--- a/lib/appsignal/sourcemap/supervisor.rb
+++ b/lib/appsignal/sourcemap/supervisor.rb
@@ -1,10 +1,13 @@
 # frozen_string_literal: true
 
+require "parallel"
 require "appsignal/sourcemap/uploader"
 
 module Appsignal
   module Sourcemap
     class Supervisor
+      PARALLEL_THREADS = 10
+
       def self.start
         new.start
       end
@@ -14,11 +17,9 @@ def start
 
         Appsignal.logger.info("Starting sourcemaps upload")
 
-        source_map_paths.map do |source_map_path|
-          Thread.new do
-            Uploader.upload(source_map_path)
-          end
-        end.each(&:join)
+        Parallel.each(source_map_paths, in_threads: PARALLEL_THREADS) do |source_map_path|
+          Uploader.upload(source_map_path)
+        end
 
         Appsignal.logger.info("Finished sourcemaps upload")
       end