diff --git a/Gemfile b/Gemfile
index a56702fad..e0980c072 100644
--- a/Gemfile
+++ b/Gemfile
@@ -75,7 +75,6 @@ gem 'premailer-rails'
 gem 'rack-attack', '~> 6.6'
 gem 'rack-cors', '~> 2.0', require: 'rack/cors'
 gem 'rails-i18n', '~> 7.0'
-gem 'rails-settings-cached', '~> 0.6', git: 'https://github.com/mastodon/rails-settings-cached.git', branch: 'v0.6.6-aliases-true'
 gem 'redcarpet', '~> 3.6'
 gem 'redis', '~> 4.5', require: ['redis', 'redis/connection/hiredis']
 gem 'mario-redis-lock', '~> 1.2', require: 'redis_lock'
diff --git a/Gemfile.lock b/Gemfile.lock
index 442022e81..50a6412a1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -18,14 +18,6 @@ GIT
       sidekiq (>= 3.5)
       statsd-ruby (~> 1.4, >= 1.4.0)
 
-GIT
-  remote: https://github.com/mastodon/rails-settings-cached.git
-  revision: 86328ef0bd04ce21cc0504ff5e334591e8c2ccab
-  branch: v0.6.6-aliases-true
-  specs:
-    rails-settings-cached (0.6.6)
-      rails (>= 4.2.0)
-
 GIT
   remote: https://github.com/stanhu/omniauth-cas.git
   revision: 4211e6d05941b4a981f9a36b49ec166cecd0e271
@@ -922,7 +914,6 @@ DEPENDENCIES
   rails (~> 7.1.1)
   rails-controller-testing (~> 1.0)
   rails-i18n (~> 7.0)
-  rails-settings-cached (~> 0.6)!
   rdf-normalize (~> 0.5)
   redcarpet (~> 3.6)
   redis (~> 4.5)
diff --git a/app/models/setting.rb b/app/models/setting.rb
index 3bdc6ffb4..ecd9d2d73 100644
--- a/app/models/setting.rb
+++ b/app/models/setting.rb
@@ -13,49 +13,120 @@
 #  thing_id   :bigint(8)
 #
 
-class Setting < RailsSettings::Base
-  source Rails.root.join('config', 'settings.yml')
+# This file is derived from a fork of the `rails-settings-cached` gem available at
+# https://github.com/mastodon/rails-settings-cached/tree/v0.6.6-aliases-true, with
+# the original available at:
+# https://github.com/huacnlee/rails-settings-cached/tree/0.x
+
+# It is licensed as follows:
+
+# Copyright (c) 2006 Alex Wayne
+# Some additional features added 2009 by Georg Ledermann
+
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+
+# The above copyright notice and this permission notice shall be
+# included in all copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOa AND
+# NONINFRINGEMENT. IN NO EVENT SaALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+class Setting < ApplicationRecord
+  after_commit :rewrite_cache, on: %i(create update)
+  after_commit :expire_cache, on: %i(destroy)
+
+  # Settings are server-wide settings only, but they were previously
+  # used for users too. This can be dropped later with a database
+  # migration dropping any scoped setting.
+  default_scope { where(thing_type: nil, thing_id: nil) }
+
+  class << self
+    # get or set a variable with the variable as the called method
+    # rubocop:disable Style/MissingRespondToMissing
+    def method_missing(method, *args)
+      # set a value for a variable
+      if method.end_with?('=')
+        var_name = method.to_s.chomp('=')
+        value = args.first
+        self[var_name] = value
+      else
+        # retrieve a value
+        self[method.to_s]
+      end
+    end
+    # rubocop:enable Style/MissingRespondToMissing
+
+    def object(var_name)
+      find_by(var: var_name.to_s)
+    end
+
+    def cache_prefix_by_startup
+      @cache_prefix_by_startup ||= Digest::MD5.hexdigest(default_settings.to_s)
+    end
+
+    def cache_key(var_name)
+      "rails_settings_cached/#{cache_prefix_by_startup}/#{var_name}"
+    end
+
+    def [](key)
+      Rails.cache.fetch(cache_key(key)) do
+        db_val = object(key)
+        db_val ? db_val.value : default_settings[key]
+      end
+    end
+
+    # set a setting value by [] notation
+    def []=(var_name, value)
+      var_name = var_name.to_s
+
+      record = object(var_name) || new(var: var_name)
+      record.value = value
+      record.save!
+    end
+
+    def default_settings
+      return @default_settings if defined?(@default_settings)
+
+      content = Rails.root.join('config', 'settings.yml').read
+      hash = content.empty? ? {} : YAML.safe_load(ERB.new(content).result, aliases: true).to_hash
+      @default_settings = hash[Rails.env] || {}
+    end
+  end
+
+  # get the value field, YAML decoded
+  def value
+    YAML.safe_load(self[:value], permitted_classes: [ActiveSupport::HashWithIndifferentAccess, Symbol]) if self[:value].present?
+  end
+
+  # set the value field, YAML encoded
+  def value=(new_value)
+    self[:value] = new_value.to_yaml
+  end
+
+  def rewrite_cache
+    Rails.cache.write(cache_key, value)
+  end
+
+  def expire_cache
+    Rails.cache.delete(cache_key)
+  end
+
+  def cache_key
+    self.class.cache_key(var)
+  end
 
   def to_param
     var
   end
-
-  class << self
-    def [](key)
-      return super(key) unless rails_initialized?
-
-      Rails.cache.fetch(cache_key(key, nil)) do
-        db_val = object(key)
-
-        if db_val
-          default_value = default_settings[key]
-
-          return default_value.with_indifferent_access.merge!(db_val.value) if default_value.is_a?(Hash)
-
-          db_val.value
-        else
-          default_settings[key]
-        end
-      end
-    end
-
-    def all_as_records
-      vars    = thing_scoped
-      records = vars.index_by(&:var)
-
-      default_settings.each do |key, default_value|
-        next if records.key?(key) || default_value.is_a?(Hash)
-
-        records[key] = Setting.new(var: key, value: default_value)
-      end
-
-      records
-    end
-
-    def default_settings
-      return {} unless RailsSettings::Default.enabled?
-
-      RailsSettings::Default.instance
-    end
-  end
 end
diff --git a/spec/models/setting_spec.rb b/spec/models/setting_spec.rb
index e98062810..ca9c65511 100644
--- a/spec/models/setting_spec.rb
+++ b/spec/models/setting_spec.rb
@@ -13,189 +13,71 @@ RSpec.describe Setting do
   end
 
   describe '.[]' do
+    let(:key)         { 'key' }
+    let(:cache_key)   { 'cache-key' }
+    let(:cache_value) { 'cache-value' }
+
     before do
-      allow(described_class).to receive(:rails_initialized?).and_return(rails_initialized)
+      allow(described_class).to receive(:cache_key).with(key).and_return(cache_key)
     end
 
-    let(:key) { 'key' }
-
-    context 'when rails_initialized? is falsey' do
-      let(:rails_initialized) { false }
-
-      it 'calls RailsSettings::Base#[]' do
-        allow(RailsSettings::Base).to receive(:[]).with(key)
-
-        described_class[key]
-
-        expect(RailsSettings::Base).to have_received(:[]).with(key)
-      end
-    end
-
-    context 'when rails_initialized? is truthy' do
+    context 'when Rails.cache does not exists' do
       before do
-        allow(RailsSettings::Base).to receive(:cache_key).with(key, nil).and_return(cache_key)
+        allow(described_class).to receive(:object).with(key).and_return(object)
+        allow(described_class).to receive(:default_settings).and_return(default_settings)
+
+        Fabricate(:setting, var: key, value: nil)
+
+        Rails.cache.delete(cache_key)
       end
 
-      let(:rails_initialized) { true }
-      let(:cache_key)         { 'cache-key' }
-      let(:cache_value)       { 'cache-value' }
+      let(:object)           { nil }
+      let(:default_value)    { 'default_value' }
+      let(:default_settings) { { key => default_value } }
 
-      it 'calls not RailsSettings::Base#[]' do
-        allow(RailsSettings::Base).to receive(:[]).with(key)
+      it 'calls Setting.object' do
+        allow(described_class).to receive(:object).with(key)
 
         described_class[key]
 
-        expect(RailsSettings::Base).to_not have_received(:[]).with(key)
+        expect(described_class).to have_received(:object).with(key)
       end
 
-      context 'when Rails.cache does not exists' do
-        before do
-          allow(RailsSettings::Settings).to receive(:object).with(key).and_return(object)
-          allow(described_class).to receive(:default_settings).and_return(default_settings)
-          settings_double = instance_double(Settings::ScopedSettings, thing_scoped: records)
-          allow(Settings::ScopedSettings).to receive(:new).and_return(settings_double)
-          Rails.cache.delete(cache_key)
+      context 'when Setting.object returns truthy' do
+        let(:object) { db_val }
+        let(:db_val) { instance_double(described_class, value: 'db_val') }
+        let(:default_value) { 'default_value' }
+
+        it 'returns db_val.value' do
+          expect(described_class[key]).to be db_val.value
         end
+      end
 
-        let(:object)           { nil }
-        let(:default_value)    { 'default_value' }
-        let(:default_settings) { { key => default_value } }
-        let(:records)          { [Fabricate(:setting, var: key, value: nil)] }
+      context 'when Setting.object returns falsey' do
+        let(:object) { nil }
 
-        it 'calls RailsSettings::Settings.object' do
-          allow(RailsSettings::Settings).to receive(:object).with(key)
+        it 'returns default_settings[key]' do
+          expect(described_class[key]).to be default_settings[key]
+        end
+      end
+    end
 
+    context 'when Rails.cache exists' do
+      before do
+        Rails.cache.write(cache_key, cache_value)
+      end
+
+      it 'does not query the database' do
+        callback = double
+        allow(callback).to receive(:call)
+        ActiveSupport::Notifications.subscribed callback, 'sql.active_record' do
           described_class[key]
-
-          expect(RailsSettings::Settings).to have_received(:object).with(key)
-        end
-
-        context 'when RailsSettings::Settings.object returns truthy' do
-          let(:object) { db_val }
-          let(:db_val) { instance_double(described_class, value: 'db_val') }
-
-          context 'when default_value is a Hash' do
-            let(:default_value) { { default_value: 'default_value' } }
-
-            it 'calls default_value.with_indifferent_access.merge!' do
-              indifferent_hash = instance_double(Hash, merge!: nil)
-              allow(default_value).to receive(:with_indifferent_access).and_return(indifferent_hash)
-
-              described_class[key]
-
-              expect(default_value).to have_received(:with_indifferent_access)
-              expect(indifferent_hash).to have_received(:merge!).with(db_val.value)
-            end
-          end
-
-          context 'when default_value is not a Hash' do
-            let(:default_value) { 'default_value' }
-
-            it 'returns db_val.value' do
-              expect(described_class[key]).to be db_val.value
-            end
-          end
-        end
-
-        context 'when RailsSettings::Settings.object returns falsey' do
-          let(:object) { nil }
-
-          it 'returns default_settings[key]' do
-            expect(described_class[key]).to be default_settings[key]
-          end
         end
+        expect(callback).to_not have_received(:call)
       end
 
-      context 'when Rails.cache exists' do
-        before do
-          Rails.cache.write(cache_key, cache_value)
-        end
-
-        it 'does not query the database' do
-          callback = double
-          allow(callback).to receive(:call)
-          ActiveSupport::Notifications.subscribed callback, 'sql.active_record' do
-            described_class[key]
-          end
-          expect(callback).to_not have_received(:call)
-        end
-
-        it 'returns the cached value' do
-          expect(described_class[key]).to eq cache_value
-        end
-      end
-    end
-  end
-
-  describe '.all_as_records' do
-    before do
-      settings_double = instance_double(Settings::ScopedSettings, thing_scoped: records)
-      allow(Settings::ScopedSettings).to receive(:new).and_return(settings_double)
-      allow(described_class).to receive(:default_settings).and_return(default_settings)
-    end
-
-    let(:key)              { 'key' }
-    let(:default_value)    { 'default_value' }
-    let(:default_settings) { { key => default_value } }
-    let(:original_setting) { Fabricate(:setting, var: key, value: nil) }
-    let(:records)          { [original_setting] }
-
-    it 'returns a Hash' do
-      expect(described_class.all_as_records).to be_a Hash
-    end
-
-    context 'when records includes Setting with var as the key' do
-      let(:records) { [original_setting] }
-
-      it 'includes the original Setting' do
-        setting = described_class.all_as_records[key]
-        expect(setting).to eq original_setting
-      end
-    end
-
-    context 'when records includes nothing' do
-      let(:records) { [] }
-
-      context 'when default_value is not a Hash' do
-        it 'includes Setting with value of default_value' do
-          setting = described_class.all_as_records[key]
-
-          expect(setting).to be_a described_class
-          expect(setting).to have_attributes(var: key)
-          expect(setting).to have_attributes(value: 'default_value')
-        end
-      end
-
-      context 'when default_value is a Hash' do
-        let(:default_value) { { 'foo' => 'fuga' } }
-
-        it 'returns {}' do
-          expect(described_class.all_as_records).to eq({})
-        end
-      end
-    end
-  end
-
-  describe '.default_settings' do
-    subject { described_class.default_settings }
-
-    before do
-      allow(RailsSettings::Default).to receive(:enabled?).and_return(enabled)
-    end
-
-    context 'when RailsSettings::Default.enabled? is false' do
-      let(:enabled) { false }
-
-      it 'returns {}' do
-        expect(subject).to eq({})
-      end
-    end
-
-    context 'when RailsSettings::Settings.enabled? is true' do
-      let(:enabled) { true }
-
-      it 'returns instance of RailsSettings::Default' do
-        expect(subject).to be_a RailsSettings::Default
+      it 'returns the cached value' do
+        expect(described_class[key]).to eq cache_value
       end
     end
   end