diff --git a/config/postal.defaults.yml b/config/postal.defaults.yml
index d863725..5f3eb32 100644
--- a/config/postal.defaults.yml
+++ b/config/postal.defaults.yml
@@ -34,6 +34,7 @@ main_db:
   username: postal
   password:
   database: postal
+  pool_size: 5
 
 logging:
   stdout: false
diff --git a/lib/postal/config.rb b/lib/postal/config.rb
index 314319e..b0cb9ca 100644
--- a/lib/postal/config.rb
+++ b/lib/postal/config.rb
@@ -74,7 +74,7 @@ module Postal
 
   def self.database_url
     if config.main_db
-      "mysql2://#{CGI.escape(config.main_db.username.to_s)}:#{CGI.escape(config.main_db.password.to_s)}@#{config.main_db.host}:#{config.main_db.port}/#{config.main_db.database}?reconnect=true&encoding=#{config.main_db.encoding || 'utf8mb4'}"
+      "mysql2://#{CGI.escape(config.main_db.username.to_s)}:#{CGI.escape(config.main_db.password.to_s)}@#{config.main_db.host}:#{config.main_db.port}/#{config.main_db.database}?reconnect=true&encoding=#{config.main_db.encoding || 'utf8mb4'}&pool=#{config.main_db.pool_size}"
     else
       "mysql2://root@localhost/postal"
     end