diff --git a/lib/chef-vault/item_keys.rb b/lib/chef-vault/item_keys.rb
index c706d5c..6927255 100644
--- a/lib/chef-vault/item_keys.rb
+++ b/lib/chef-vault/item_keys.rb
@@ -28,9 +28,33 @@ def initialize(vault, name)
       @raw_data["admins"] = []
       @raw_data["clients"] = []
       @raw_data["search_query"] = []
+      @raw_data["mode"] = "default"
+      @cache = {} # write-back cache for keys
+    end
+
+    def [](key)
+      # return options immediately
+      return @raw_data[key] if %w{id admins clients search_query mode}.include?(key)
+      # check if the key is in the write-back cache
+      ckey = @cache[key]
+      return ckey unless ckey.nil?
+      # check if the key is saved in sparse mode
+      skey = sparse_key(sparse_id(key))
+      if skey
+        skey[key]
+      else
+        # fallback to raw data
+        @raw_data[key]
+      end
     end
 
     def include?(key)
+      # check if the key is in the write-back cache
+      ckey = @cache[key]
+      return (ckey ? true : false) unless ckey.nil?
+      # check if the key is saved in sparse mode
+      return true unless sparse_key(sparse_id(key)).nil?
+      # fallback to non-sparse mode if sparse key is not found
       @raw_data.keys.include?(key)
     end
 
@@ -40,16 +64,24 @@ def add(chef_key, data_bag_shared_secret)
         raise ChefVault::Exceptions::V1Format,
               "cannot manage a v1 vault.  See UPGRADE.md for help"
       end
-      self[chef_key.name] = ChefVault::ItemKeys.encode_key(chef_key.key, data_bag_shared_secret)
+      @cache[chef_key.name] = ChefVault::ItemKeys.encode_key(chef_key.key, data_bag_shared_secret)
       @raw_data[type] << chef_key.name unless @raw_data[type].include?(chef_key.name)
       @raw_data[type]
     end
 
     def delete(chef_key)
-      raw_data.delete(chef_key.name)
+      @cache[chef_key.name] = false
       raw_data[chef_key.type].delete(chef_key.name)
     end
 
+    def mode(mode = nil)
+      if mode
+        @raw_data["mode"] = mode
+      else
+        @raw_data["mode"]
+      end
+    end
+
     def search_query(search_query = nil)
       if search_query
         @raw_data["search_query"] = search_query
@@ -67,9 +99,8 @@ def admins
     end
 
     def save(item_id = @raw_data["id"])
-      if Chef::Config[:solo_legacy_mode]
-        save_solo(item_id)
-      else
+      # create data bag if not running in solo mode
+      unless Chef::Config[:solo_legacy_mode]
         begin
           Chef::DataBag.load(data_bag)
         rescue Net::HTTPServerException => http_error
@@ -79,9 +110,53 @@ def save(item_id = @raw_data["id"])
             chef_data_bag.create
           end
         end
+      end
 
+      # write cached keys to data
+      @cache.each do |key, val|
+        # delete across all modes on key deletion
+        if val == false
+          # sparse mode key deletion
+          if Chef::Config[:solo_legacy_mode]
+            delete_solo(sparse_id(key))
+          else
+            begin
+              Chef::DataBagItem.from_hash("data_bag" => data_bag,
+                                          "id" => sparse_id(key))
+                               .destroy(data_bag, sparse_id(key))
+            rescue Net::HTTPServerException => http_error
+              raise http_error unless http_error.response.code == "404"
+            end
+          end
+          # default mode key deletion
+          @raw_data.delete(key)
+        else
+          if @raw_data["mode"] == "sparse"
+            # sparse mode key creation
+            skey = Chef::DataBagItem.from_hash(
+              "data_bag" => data_bag,
+              "id" => sparse_id(key),
+              key => val
+            )
+            if Chef::Config[:solo_legacy_mode]
+              save_solo(skey.id, skey.raw_data)
+            else
+              skey.save
+            end
+          else
+            # default mode key creation
+            @raw_data[key] = val
+          end
+        end
+      end
+      # save raw data
+      if Chef::Config[:solo_legacy_mode]
+        save_solo(item_id)
+      else
         super
       end
+      # clear write-back cache
+      @cache = {}
     end
 
     def destroy
@@ -129,6 +204,22 @@ def self.load(vault, name)
 
     # @private
 
+    def sparse_id(key, item_id = @raw_data["id"])
+      "#{item_id}_key_#{key}"
+    end
+
+    def sparse_key(sid)
+      if Chef::Config[:solo_legacy_mode]
+        load_solo(sid)
+      else
+        begin
+          Chef::DataBagItem.load(@data_bag, sid)
+        rescue Net::HTTPServerException => http_error
+          nil if http_error.response.code == "404"
+        end
+      end
+    end
+
     def self.encode_key(key_string, data_bag_shared_secret)
       public_key = OpenSSL::PKey::RSA.new(key_string)
       Base64.encode64(public_key.public_encrypt(data_bag_shared_secret))
diff --git a/lib/chef-vault/mixins.rb b/lib/chef-vault/mixins.rb
index 8071115..f11e9e7 100644
--- a/lib/chef-vault/mixins.rb
+++ b/lib/chef-vault/mixins.rb
@@ -22,7 +22,7 @@ def find_solo_path(item_id)
       [data_bag_path, data_bag_item_path]
     end
 
-    def save_solo(item_id = @raw_data["id"])
+    def save_solo(item_id = @raw_data["id"], raw_data = @raw_data)
       data_bag_path, data_bag_item_path = find_solo_path(item_id)
 
       FileUtils.mkdir(data_bag_path) unless File.exist?(data_bag_path)
@@ -32,5 +32,15 @@ def save_solo(item_id = @raw_data["id"])
 
       raw_data
     end
+
+    def delete_solo(item_id = @raw_data["id"])
+      _data_bag_path, data_bag_item_path = find_solo_path(item_id)
+      FileUtils.rm(data_bag_item_path) if File.exist?(data_bag_item_path)
+    end
+
+    def load_solo(item_id = @raw_data["id"])
+      _data_bag_path, data_bag_item_path = find_solo_path(item_id)
+      JSON.parse(File.read(data_bag_item_path)) if File.exist?(data_bag_item_path)
+    end
   end
 end
diff --git a/spec/chef-vault/item_keys_spec.rb b/spec/chef-vault/item_keys_spec.rb
index 45d6cff..9820064 100644
--- a/spec/chef-vault/item_keys_spec.rb
+++ b/spec/chef-vault/item_keys_spec.rb
@@ -2,6 +2,9 @@
   describe "#new" do
     let(:keys) { ChefVault::ItemKeys.new("foo", "bar") }
     let(:shared_secret) { "super_secret" }
+    let(:public_key_string) do
+      "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyMXT9IOV9pkQsxsnhSx8\n8RX6GW3caxkjcXFfHg6E7zUVBFAsfw4B1D+eHAks3qrDB7UrUxsmCBXwU4dQHaQy\ngAn5Sv0Jc4CejDNL2EeCBLZ4TF05odHmuzyDdPkSZP6utpR7+uF7SgVQedFGySIB\nih86aM+HynhkJqgJYhoxkrdo/JcWjpk7YEmWb6p4esnvPWOpbcjIoFs4OjavWBOF\niTfpkS0SkygpLi/iQu9RQfd4hDMWCc6yh3Th/1nVMUd+xQCdUK5wxluAWSv8U0zu\nhiIlZNazpCGHp+3QdP3f6rebmQA8pRM8qT5SlOvCYPk79j+IMUVSYrR4/DTZ+VM+\naQIDAQAB\n-----END PUBLIC KEY-----\n"
+    end
 
     it "'foo' is assigned to @data_bag" do
       expect(keys.data_bag).to eq "foo"
@@ -19,10 +22,7 @@
       expect(keys["admins"]).to eq []
     end
 
-    describe "key mgmt operations" do
-      let(:public_key_string) do
-        "-----BEGIN PUBLIC KEY-----\nMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyMXT9IOV9pkQsxsnhSx8\n8RX6GW3caxkjcXFfHg6E7zUVBFAsfw4B1D+eHAks3qrDB7UrUxsmCBXwU4dQHaQy\ngAn5Sv0Jc4CejDNL2EeCBLZ4TF05odHmuzyDdPkSZP6utpR7+uF7SgVQedFGySIB\nih86aM+HynhkJqgJYhoxkrdo/JcWjpk7YEmWb6p4esnvPWOpbcjIoFs4OjavWBOF\niTfpkS0SkygpLi/iQu9RQfd4hDMWCc6yh3Th/1nVMUd+xQCdUK5wxluAWSv8U0zu\nhiIlZNazpCGHp+3QdP3f6rebmQA8pRM8qT5SlOvCYPk79j+IMUVSYrR4/DTZ+VM+\naQIDAQAB\n-----END PUBLIC KEY-----\n"
-      end
+    shared_context "key mgmt operations" do
 
       shared_examples_for "proper key management" do
         let(:chef_key) { ChefVault::Actor.new(type, name) }
@@ -41,6 +41,7 @@
             keys.add(chef_key, shared_secret)
             expect(keys[name]).to eq("encrypted_result")
             expect(keys[type].include?(name)).to eq(true)
+            expect(keys.include?(name)).to eq(true)
           end
         end
 
@@ -53,6 +54,7 @@
             keys.delete(chef_key)
             expect(keys.has_key?(chef_key.name)).to eq(false)
             expect(keys[type].include?(name)).to eq(false)
+            expect(keys.include?(name)).to eq(false)
           end
         end
       end
@@ -75,10 +77,37 @@
       before { server.start_background }
       after  { server.stop }
 
+      include_context "key mgmt operations"
+
       describe "#save" do
+        let(:client_name) { "client_name" }
+        let(:chef_key)    { ChefVault::Actor.new("clients", client_name) }
+
+        before do
+          allow(chef_key).to receive(:key) { public_key_string }
+        end
+
         it "should save the key data" do
+          keys.add(chef_key, shared_secret)
           keys.save("bar")
           expect(Chef::DataBagItem.load("foo", "bar").to_hash).to include("id" => "bar")
+          expect(keys[client_name]).not_to be_empty
+          keys.delete(chef_key)
+          keys.save("bar")
+          expect(keys[client_name]).to be_nil
+        end
+
+        it "should save the key data in sparse mode" do
+          keys.add(chef_key, shared_secret)
+          keys.mode("sparse")
+          keys.save("bar")
+          expect(Chef::DataBagItem.load("foo", "bar").to_hash).to include("id" => "bar")
+          expect(Chef::DataBagItem.load("foo", "bar_key_client_name").to_hash).to include("id" => "bar_key_client_name")
+          expect(keys[client_name]).not_to be_empty
+          keys.delete(chef_key)
+          keys.save("bar")
+          expect(keys[client_name]).to be_nil
+          keys.mode("default")
         end
       end
     end
@@ -87,6 +116,8 @@
       before { Chef::Config[:solo_legacy_mode] = true  }
       after  { Chef::Config[:solo_legacy_mode] = false }
 
+      include_context "key mgmt operations"
+
       describe "#find_solo_path" do
         context "when data_bag_path is an array" do
           before do
@@ -119,15 +150,36 @@
       end
 
       describe "#save" do
+        let(:client_name)   { "client_name" }
+        let(:chef_key)      { ChefVault::Actor.new("clients", client_name) }
         let(:data_bag_path) { Dir.mktmpdir("vault_item_keys") }
+
         before do
           Chef::Config[:data_bag_path] = data_bag_path
+          allow(chef_key).to receive(:key) { public_key_string }
         end
 
         it "should save the key data" do
-          expect(File).to receive(:exist?).with(File.join(data_bag_path, "foo")).and_call_original
+          keys.add(chef_key, shared_secret)
           keys.save("bar")
           expect(File.read(File.join(data_bag_path, "foo", "bar.json"))).to match(/"id":.*"bar"/)
+          expect(keys[client_name]).not_to be_empty
+          keys.delete(chef_key)
+          keys.save("bar")
+          expect(keys[client_name]).to be_nil
+        end
+
+        it "should save the key data in sparse mode" do
+          keys.add(chef_key, shared_secret)
+          keys.mode("sparse")
+          keys.save("bar")
+          expect(File.read(File.join(data_bag_path, "foo", "bar.json"))).to match(/"id":.*"bar"/)
+          expect(File.read(File.join(data_bag_path, "foo", "bar_key_client_name.json"))).to match(/"id":.*"bar_key_client_name"/)
+          expect(keys[client_name]).not_to be_empty
+          keys.delete(chef_key)
+          keys.save("bar")
+          expect(keys[client_name]).to be_nil
+          keys.mode("default")
         end
       end
     end