diff --git a/Gemfile b/Gemfile
index ee256912..5c281642 100644
--- a/Gemfile
+++ b/Gemfile
@@ -20,7 +20,6 @@ gem 'puma', '~> 3.0'
 gem 'responders', '~> 2.0'
 
 # as supported databases
-gem 'mysql2'
 gem 'pg'
 
 # for tracking data changes
@@ -143,8 +142,7 @@ gem 'rqrcode'
 gem 'axlsx', git: 'https://github.com/randym/axlsx.git'
 gem 'axlsx_rails'
 
-# as error catcher
-gem 'airbrake'
+gem 'sentry'
 
 # to make links faster
 gem 'turbolinks'
diff --git a/Gemfile.lock b/Gemfile.lock
index 519ea1ab..be766571 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -68,10 +68,6 @@ GEM
     addressable (2.6.0)
       public_suffix (>= 2.0.2, < 4.0)
     afm (0.2.2)
-    airbrake (9.2.2)
-      airbrake-ruby (~> 4.4)
-    airbrake-ruby (4.4.0)
-      rbtree3 (~> 0.5)
     ajax-datatables-rails (0.4.3)
       railties (>= 4.0)
     archive-zip (0.12.0)
@@ -303,7 +299,6 @@ GEM
     multi_json (1.13.1)
     multi_xml (0.6.0)
     multipart-post (2.1.1)
-    mysql2 (0.5.3)
     nenv (0.3.0)
     netrc (0.11.0)
     nio4r (2.5.2)
@@ -440,7 +435,6 @@ GEM
     rb-fsevent (0.10.3)
     rb-inotify (0.10.0)
       ffi (~> 1.0)
-    rbtree3 (0.5.0)
     rdoc (6.0.4)
     rdoc-generator-fivefish (0.4.0)
       inversion (~> 1.1)
@@ -524,6 +518,7 @@ GEM
     selenium-webdriver (3.142.6)
       childprocess (>= 0.5, < 4.0)
       rubyzip (>= 1.2.2)
+    sentry (0.5.3)
     sexp_processor (4.11.0)
     shellany (0.0.1)
     shoulda-matchers (4.1.2)
@@ -613,7 +608,6 @@ DEPENDENCIES
   active_model_serializers
   acts_as_commentable_with_threading
   acts_as_list
-  airbrake
   ajax-datatables-rails
   autoprefixer-rails
   awesome_nested_set
@@ -662,7 +656,6 @@ DEPENDENCIES
   mina
   mini_magick
   money-rails
-  mysql2
   nokogiri (>= 1.8.1)
   omniauth
   omniauth-discourse
@@ -705,6 +698,7 @@ DEPENDENCIES
   ruby-oembed
   sass-rails (>= 4.0.2)
   selectize-rails
+  sentry
   shoulda-matchers
   skylight
   spring-commands-rspec