diff --git a/.rspec b/.rspec
new file mode 100644
index 0000000..c99d2e7
--- /dev/null
+++ b/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/.rubocop.yml b/.rubocop.yml
index 63cd12d..67ac226 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,10 +1,21 @@
-inherit_from: .rubocop_todo.yml
-
-Documentation:
-  Enabled: false
+AllCops:
+  NewCops: enable
+  TargetRubyVersion: 2.6
 
 Layout/BlockAlignment:
   EnforcedStyleAlignWith: start_of_block
 
 Layout/MultilineMethodCallIndentation:
   EnforcedStyle: indented_relative_to_receiver
+
+Metrics/BlockLength:
+  ExcludedMethods:
+    - context
+    - describe
+
+Naming/FileName:
+  Exclude:
+    - 'lib/grape-cache.rb'
+
+Style/FrozenStringLiteralComment:
+  SafeAutoCorrect: true
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
deleted file mode 100644
index 9d2eeaa..0000000
--- a/.rubocop_todo.yml
+++ /dev/null
@@ -1,30 +0,0 @@
-# This configuration was generated by
-# `rubocop --auto-gen-config`
-# on 2019-11-01 20:51:53 +0300 using RuboCop version 0.74.0.
-# The point is for the user to remove these configuration records
-# one by one as the offenses are removed from the code base.
-# Note that changes in the inspected code, or installation of new
-# versions of RuboCop, may require this file to be generated again.
-
-# Offense count: 1
-Metrics/AbcSize:
-  Max: 16
-
-# Offense count: 1
-# Configuration parameters: CountComments, ExcludedMethods.
-Metrics/MethodLength:
-  Max: 11
-
-# Offense count: 1
-# Configuration parameters: ExpectMatchingDefinition, Regex, IgnoreExecutableScripts, AllowedAcronyms.
-# AllowedAcronyms: CLI, DSL, ACL, API, ASCII, CPU, CSS, DNS, EOF, GUID, HTML, HTTP, HTTPS, ID, IP, JSON, LHS, QPS, RAM, RHS, RPC, SLA, SMTP, SQL, SSH, TCP, TLS, TTL, UDP, UI, UID, UUID, URI, URL, UTF8, VM, XML, XMPP, XSRF, XSS
-Naming/FileName:
-  Exclude:
-    - 'lib/grape-cache.rb'
-
-# Offense count: 5
-# Cop supports --auto-correct.
-# Configuration parameters: AutoCorrect, AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
-# URISchemes: http, https
-Metrics/LineLength:
-  Max: 98
diff --git a/Gemfile b/Gemfile
index 7f4f5e9..a330751 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,3 +3,14 @@
 source 'https://rubygems.org'
 
 gemspec
+
+group :development, :test do
+  gem 'bundler'
+  gem 'pry', '~> 0.13.1'
+  gem 'rubocop', '~> 1.18.0'
+end
+
+group :test do
+  gem 'rspec', '~> 3.10.0'
+  gem 'rack-test', '~> 1.1.0'
+end
diff --git a/grape-cache.gemspec b/grape-cache.gemspec
index 1a11909..1bc88d7 100644
--- a/grape-cache.gemspec
+++ b/grape-cache.gemspec
@@ -20,15 +20,13 @@ Gem::Specification.new do |spec|
   spec.require_path = 'lib'
 
   spec.metadata = {
-    'bug_tracker_uri'   => 'https://github.com/netrusov/grape-cache/issues',
-    'source_code_uri'   => 'https://github.com/netrusov/grape-cache'
+    'bug_tracker_uri' => 'https://github.com/netrusov/grape-cache/issues',
+    'source_code_uri' => 'https://github.com/netrusov/grape-cache'
   }
 
+  spec.required_ruby_version = '>= 2.6.0'
+
   spec.add_runtime_dependency 'activesupport'
   spec.add_runtime_dependency 'grape', '>= 1.2', '< 2'
   spec.add_runtime_dependency 'rack'
-
-  spec.add_development_dependency 'bundler'
-  spec.add_development_dependency 'pry'
-  spec.add_development_dependency 'rubocop'
 end
diff --git a/lib/grape/cache.rb b/lib/grape/cache.rb
index f205cee..3e34e8a 100644
--- a/lib/grape/cache.rb
+++ b/lib/grape/cache.rb
@@ -1,44 +1,80 @@
 # frozen_string_literal: true
 
-require 'rack'
 require 'grape'
+require 'rack'
+
+require 'active_support/cache'
+require 'active_support/concern'
+require 'active_support/notifications'
 
 require 'grape/cache/configurable'
-require 'grape/cache/extensions/dsl'
-require 'grape/cache/extensions/endpoint'
-require 'grape/cache/helpers'
+require 'grape/cache/dsl'
 require 'grape/cache/version'
 
+require 'grape/cache/extensions/dsl'
+require 'grape/cache/extensions/instance'
+require 'grape/cache/extensions/middleware/formatter'
+
 module Grape
+  # @nodoc
   module Cache
     include Grape::Cache::Configurable
 
     # @param key [String] cache key
-    # @return [Object] response object
+    # @return [String] serialized response object
     def self.read(key)
-      config
-        .backend
-        .read(key)
-        .then { |result| Grape::Json.load(result) if result }
+      config.backend.read(key)
     end
 
     # @param key [String] cache key
-    # @param response [Object] response object
+    # @param value [Object] response object
     # @param options [Object] (see ActiveSupport::Cache#write)
     # @return [Boolean] operation status
-    def self.store(key, response, options)
-      return false unless response
+    def self.write(key, value, options)
+      return false unless value
+
+      options = options.except(:expires_in) if options[:expires_in]&.<=(0)
 
-      Grape::Json
-        .dump(response)
-        .then { |value| config.backend.write(key, value, options) }
+      config.backend.write(key, value, options)
+    rescue StandardError => e
+      ActiveSupport::Notifications.instrument('grape_cache.write_error', error: e)
+      false
     end
-  end
-end
 
-Grape::API::Instance.class_exec do
-  include Grape::Cache::Extensions::DSL
-  include Grape::Cache::Extensions::Endpoint
+    # @param env [Object] request env
+    # @param key [#to_s, Array<#to_s>] any object or array of objects that respond to `#to_s`
+    # @return [String] cache key
+    def self.expand_cache_key(env, key)
+      key = [
+        env[Rack::REQUEST_METHOD],
+        env[Rack::PATH_INFO],
+        '-'
+      ] + Array(key).compact
 
-  helpers Grape::Cache::Helpers
+      ActiveSupport::Cache.expand_cache_key(key)
+    end
+
+    # @param env [Object] request env
+    # @param key [String] cache key
+    # @param context [Grape::Cache::DSL] context object
+    # @yield block which will be called on cache miss
+    # @return [String, Object] returns cached response or result of executed block
+    def self.with_cached_response(env, key, context)
+      env['grape-cache'] = { key: key }
+
+      if (value = Grape::Cache.read(key))
+        env['grape-cache'][:hit] = true
+        env['grape-cache'][:value] = value
+      else
+        env['grape-cache'][:hit] = false
+        env['grape-cache'][:options] = context.slice(:expires_in, :race_condition_ttl).compact
+
+        yield
+      end
+    end
+  end
 end
+
+Grape::API::Instance.include(Grape::Cache::Extensions::DSL)
+Grape::API::Instance.include(Grape::Cache::Extensions::Instance)
+Grape::Middleware::Formatter.prepend(Grape::Cache::Extensions::Middleware::Formatter)
diff --git a/lib/grape/cache/configurable.rb b/lib/grape/cache/configurable.rb
index 1a3c6cf..7028305 100644
--- a/lib/grape/cache/configurable.rb
+++ b/lib/grape/cache/configurable.rb
@@ -1,13 +1,12 @@
 # frozen_string_literal: true
 
-require 'active_support/cache'
-require 'active_support/concern'
-
 module Grape
   module Cache
+    # @nodoc
     module Configurable
       extend ActiveSupport::Concern
 
+      # @nodoc
       class Configuration
         attr_accessor :backend
 
diff --git a/lib/grape/cache/dsl.rb b/lib/grape/cache/dsl.rb
index e22adfb..bc10550 100644
--- a/lib/grape/cache/dsl.rb
+++ b/lib/grape/cache/dsl.rb
@@ -2,6 +2,7 @@
 
 module Grape
   module Cache
+    # @nodoc
     class DSL
       # @private
       class CacheControl
@@ -10,7 +11,7 @@ def initialize(options = {})
         end
 
         def max_age
-          @options[:max_age]
+          @options[:max_age].to_i
         end
 
         def public?
@@ -26,44 +27,48 @@ def no_cache?
         end
 
         def to_s
-          options = []
-
-          options << (public? ? 'public' : 'private')
-          options << (no_cache? ? 'no-cache' : ['max-age', max_age].join('='))
-          options << 'must-revalidate' if must_revalidate?
-
-          options.join(', ')
+          [
+            (public? ? 'public' : 'private'),
+            (no_cache? ? 'no-cache' : "max-age=#{max_age}"),
+            ('must-revalidate' if must_revalidate?)
+          ].compact.join(', ')
         end
       end
 
-      delegate :[], :[]=, :fetch, to: :@storage
+      delegate :[], :slice, to: :@store
 
       def initialize
-        @storage = {
+        @store = {
           expires_in: 0,
-          cache_control: 'private, max-age=0, must-revalidate'
+          race_condition_ttl: 5,
+          cache_control: 'private, no-cache, must-revalidate'
         }
       end
 
       # @return [void]
       def key(value = nil, &block)
-        self[:key] = value || block
+        @store[:key] = value || block
       end
 
       # @param seconds [Integer] cache TTL
       # @return [void]
       def expires_in(seconds)
-        self[:expires_in] = seconds.to_i
+        @store[:expires_in] = seconds.to_i
+      end
+
+      # @param seconds [Integer] cache race condition TTL
+      # @return [void]
+      def race_condition_ttl(seconds)
+        @store[:race_condition_ttl] = seconds.to_i
       end
 
       # @param options [Hash] parameters for "Cache-Control" header
-      # @option options :public [Boolean] defaults to "false"
+      # @option options :public [Boolean]
       # @option options :must_revalidate [Boolean]
-      # @option options :max_age [Integer] defaults to "expires_in"
+      # @option options :max_age [Integer]
       # @return [void]
       def cache_control(options = {})
-        self[:cache_control] =
-          CacheControl.new(options.reverse_merge(max_age: self[:expires_in])).to_s
+        @store[:cache_control] = CacheControl.new(options).to_s
       end
     end
   end
diff --git a/lib/grape/cache/extensions/dsl.rb b/lib/grape/cache/extensions/dsl.rb
index a3ef973..2750485 100644
--- a/lib/grape/cache/extensions/dsl.rb
+++ b/lib/grape/cache/extensions/dsl.rb
@@ -1,12 +1,9 @@
 # frozen_string_literal: true
 
-require 'active_support/concern'
-
-require 'grape/cache/dsl'
-
 module Grape
   module Cache
     module Extensions
+      # @nodoc
       module DSL
         extend ActiveSupport::Concern
 
@@ -15,10 +12,9 @@ module DSL
           #
           # @return [void]
           def cache(&block)
-            Grape::Cache::DSL.new.then do |context|
-              context.instance_exec(&block)
-              route_setting :cache, context
-            end
+            context = Grape::Cache::DSL.new
+            context.instance_exec(&block)
+            route_setting(:cache, context)
           end
         end
       end
diff --git a/lib/grape/cache/extensions/endpoint.rb b/lib/grape/cache/extensions/instance.rb
similarity index 62%
rename from lib/grape/cache/extensions/endpoint.rb
rename to lib/grape/cache/extensions/instance.rb
index f126c8d..4d292c1 100644
--- a/lib/grape/cache/extensions/endpoint.rb
+++ b/lib/grape/cache/extensions/instance.rb
@@ -3,7 +3,8 @@
 module Grape
   module Cache
     module Extensions
-      module Endpoint
+      # @nodoc
+      module Instance
         extend ActiveSupport::Concern
 
         class_methods do
@@ -15,14 +16,11 @@ def generate_cached_api_method(context, &block)
             proc do
               header 'Cache-Control', context[:cache_control]
 
-              cache_key =
-                context[:key]
-                  .then { |key| key.is_a?(Proc) ? instance_exec(&key) : key }
-                  .then { |key| expand_cache_key(*key) }
+              key = context[:key]
+              key = key.is_a?(Proc) ? instance_exec(&key) : key
+              key = Grape::Cache.expand_cache_key(env, key)
 
-              Grape::Cache.read(cache_key) || instance_exec(&block).tap do |response|
-                Grape::Cache.store cache_key, (body || response), expires_in: context[:expires_in]
-              end
+              Grape::Cache.with_cached_response(env, key, context) { instance_exec(&block) }
             end
           end
 
diff --git a/lib/grape/cache/extensions/middleware/formatter.rb b/lib/grape/cache/extensions/middleware/formatter.rb
new file mode 100644
index 0000000..c8457de
--- /dev/null
+++ b/lib/grape/cache/extensions/middleware/formatter.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Grape
+  module Cache
+    module Extensions
+      module Middleware
+        # @nodoc
+        module Formatter
+          def fetch_formatter(*)
+            formatter = super
+
+            lambda do |body, env|
+              cache = env['grape-cache']
+
+              return formatter.call(body, env) unless cache
+              return cache[:value] if cache[:hit]
+
+              formatter.call(body, env).tap do |response|
+                Grape::Cache.write(cache[:key], response, cache[:options])
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/grape/cache/helpers.rb b/lib/grape/cache/helpers.rb
deleted file mode 100644
index 074615a..0000000
--- a/lib/grape/cache/helpers.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-require 'active_support/cache'
-
-module Grape
-  module Cache
-    module Helpers
-      # @param *args [String, Integer] parameters which will be concatenated into cache key
-      # @return [String] cache key
-      def expand_cache_key(*args)
-        [
-          env.fetch(Rack::REQUEST_METHOD),
-          env.fetch(Rack::PATH_INFO),
-          '-',
-          *args
-        ].compact.then(&ActiveSupport::Cache.method(:expand_cache_key))
-      end
-    end
-  end
-end
diff --git a/lib/grape/cache/version.rb b/lib/grape/cache/version.rb
index a986667..32a1f51 100644
--- a/lib/grape/cache/version.rb
+++ b/lib/grape/cache/version.rb
@@ -2,6 +2,6 @@
 
 module Grape
   module Cache
-    VERSION = '0.2.1'
+    VERSION = '0.2.2'
   end
 end
diff --git a/spec/grape/cache/dsl_spec.rb b/spec/grape/cache/dsl_spec.rb
new file mode 100644
index 0000000..4187165
--- /dev/null
+++ b/spec/grape/cache/dsl_spec.rb
@@ -0,0 +1,102 @@
+# frozen_string_literal: true
+
+RSpec.describe Grape::Cache::DSL do
+  subject { Grape::Cache::DSL.new }
+
+  describe '#key' do
+    let(:key) { %w[foo bar baz] }
+
+    before do
+      subject.key key
+    end
+
+    it 'simply stores any value passed' do
+      expect(subject[:key]).to eq(key)
+    end
+  end
+
+  describe '#expires_in' do
+    let(:expires_in) { '60' }
+
+    before do
+      subject.expires_in expires_in
+    end
+
+    it 'converts any value to integer' do
+      expect(subject[:expires_in]).to eq(expires_in.to_i)
+    end
+  end
+
+  describe '#race_condition_ttl' do
+    let(:ttl) { '60' }
+
+    before do
+      subject.race_condition_ttl ttl
+    end
+
+    it 'converts any value to integer' do
+      expect(subject[:race_condition_ttl]).to eq(ttl.to_i)
+    end
+  end
+
+  describe '#cache_control' do
+    let(:default_value) { 'private, no-cache, must-revalidate' }
+    let(:max_age) { 1.minute }
+
+    before do
+      subject.cache_control options
+    end
+
+    context 'max-age' do
+      let(:options) { { max_age: max_age } }
+
+      it 'sets cache TTL' do
+        expect(subject[:cache_control]).to eq("private, max-age=#{max_age.to_i}")
+      end
+    end
+
+    context 'public' do
+      context 'when max-age is not set' do
+        let(:options) { { public: true } }
+
+        it 'stays private' do
+          expect(subject[:cache_control]).to eq('private, no-cache, must-revalidate')
+        end
+      end
+
+      context 'when max-age is set' do
+        let(:options) { { public: true, max_age: max_age } }
+
+        it 'becomes public' do
+          expect(subject[:cache_control]).to eq("public, max-age=#{max_age.to_i}")
+        end
+      end
+    end
+
+    context 'must-revalidate' do
+      context 'when max-age is not set' do
+        let(:options) { { must_revalidate: false } }
+
+        it 'stays present' do
+          expect(subject[:cache_control]).to eq('private, no-cache, must-revalidate')
+        end
+      end
+
+      context 'when max-age is set' do
+        let(:options) { { must_revalidate: false, max_age: max_age } }
+
+        it 'becomes absent' do
+          expect(subject[:cache_control]).to eq("private, max-age=#{max_age.to_i}")
+        end
+
+        context 'when must-revalidate is set to true' do
+          let(:options) { { must_revalidate: true, max_age: max_age } }
+
+          it 'stays present' do
+            expect(subject[:cache_control]).to eq("private, max-age=#{max_age.to_i}, must-revalidate")
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/grape/cache_spec.rb b/spec/grape/cache_spec.rb
new file mode 100644
index 0000000..9583719
--- /dev/null
+++ b/spec/grape/cache_spec.rb
@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+RSpec.describe Grape::Cache do
+  let(:backend) { ActiveSupport::Cache::MemoryStore.new }
+
+  before do
+    Grape::Cache.config.backend = backend
+  end
+
+  after { backend.cleanup }
+
+  describe '.write' do
+    let(:key) { 'key' }
+    let(:value) { 'hit' }
+    let(:options) { {} }
+
+    subject { described_class.write(key, value, options) }
+
+    after { subject }
+
+    context 'when expires_in is <= 0' do
+      let(:options) { { expires_in: 0, race_condition_ttl: 5.seconds } }
+
+      it 'removes it from the options' do
+        expect(backend).to receive(:write).with(key, value, { race_condition_ttl: 5 })
+      end
+    end
+  end
+
+  describe '.expand_cache_key' do
+    let(:app) { Class.new(Grape::API) }
+    let(:key) { %w[foo bar] }
+    let(:route) { '/users' }
+
+    subject { described_class.expand_cache_key(last_request.env, key) }
+
+    before do
+      app.get route do
+        'response'
+      end
+    end
+
+    it 'generates cache key in the following format: (<http-method>)/(<route>)/-(/<additional-arguments>)*' do
+      get route
+
+      is_expected.to eq("GET/#{route}/-/foo/bar")
+    end
+  end
+
+  describe '.with_cached_response' do
+    let(:key) { 'key' }
+    let(:backend_key) { 'not-the-right-one' }
+    let(:hit_value) { 'hit' }
+    let(:miss_value) { 'miss' }
+    let(:env) { {} }
+    let(:options) { {} }
+
+    subject do
+      described_class.with_cached_response(env, key, options) { miss_value }
+    end
+
+    before do
+      backend.write(backend_key, hit_value)
+      subject
+    end
+
+    context 'on cache miss' do
+      it 'executes block' do
+        is_expected.to eq(miss_value)
+      end
+
+      it 'sets :hit to false' do
+        expect(env['grape-cache'][:hit]).to eq(false)
+      end
+
+      it "doesn't set :value" do
+        expect(env['grape-cache'][:value]).to be_nil
+      end
+    end
+
+    context 'on cache hit' do
+      let(:backend_key) { key }
+
+      it 'returns cached value' do
+        is_expected.to eq(hit_value)
+      end
+
+      it 'sets :hit to true' do
+        expect(env['grape-cache'][:hit]).to eq(true)
+      end
+
+      it 'sets :value to cached value' do
+        expect(env['grape-cache'][:value]).to eq(hit_value)
+      end
+    end
+  end
+end
diff --git a/spec/grape/endpoint_spec.rb b/spec/grape/endpoint_spec.rb
new file mode 100644
index 0000000..4483fd8
--- /dev/null
+++ b/spec/grape/endpoint_spec.rb
@@ -0,0 +1,105 @@
+# frozen_string_literal: true
+
+RSpec.describe Grape::Endpoint do
+  let(:app) { Class.new(Grape::API) }
+  let(:backend) { ActiveSupport::Cache::MemoryStore.new }
+
+  before do
+    Grape::Cache.config.backend = backend
+  end
+
+  after { backend.cleanup }
+
+  context 'without cache' do
+    before do
+      app.get '/' do
+        rand
+      end
+    end
+
+    it "always returns different results and doesn't touch the cache" do
+      expect(backend).not_to receive(:read)
+      expect(backend).not_to receive(:write)
+
+      r1 = get('/')
+      r2 = get('/')
+
+      expect(r1.body).not_to eq(r2.body)
+    end
+  end
+
+  context 'with cache' do
+    before do
+      app.cache do
+        expires_in 1.minute
+      end
+      app.get '/' do
+        rand
+      end
+    end
+
+    it 'always returns the result of the first run' do
+      expect(backend).to receive(:read).twice.and_call_original
+      expect(backend).to receive(:write).once.and_call_original
+
+      r1 = get('/')
+      r2 = get('/')
+
+      expect(r1.body).to eq(r2.body)
+    end
+  end
+
+  context 'with different response serializers' do
+    let(:default_format) { :txt }
+    let(:helper) do
+      Module.new do
+        module_function
+
+        def data
+          {
+            k1: :v1,
+            k2: :v2
+          }
+        end
+      end
+    end
+
+    before do
+      app.default_format default_format
+      app.helpers helper
+      app.cache do
+        expires_in 1.minute
+      end
+      app.get '/' do
+        data
+      end
+    end
+
+    shared_examples 'serialized response' do
+      it 'must cache serialized response' do
+        expect(backend).to receive(:write)
+                             .once
+                             .with(kind_of(String), serialized_response, kind_of(Hash))
+                             .and_call_original
+
+        2.times { get '/' }
+
+        expect(last_response.body).to eq(serialized_response)
+      end
+    end
+
+    context 'JSON' do
+      let(:default_format) { :json }
+      let(:serialized_response) { helper.data.to_json }
+
+      it_behaves_like 'serialized response'
+    end
+
+    context 'XML' do
+      let(:default_format) { :xml }
+      let(:serialized_response) { helper.data.to_xml }
+
+      it_behaves_like 'serialized response'
+    end
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..ffe2635
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+require 'grape-cache'
+
+require 'rubygems'
+require 'bundler'
+
+Bundler.require(:default, :test)
+
+RSpec.configure do |config|
+  config.include Rack::Test::Methods
+end