diff --git a/README.md b/README.md
index 00caa09..a457faa 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ AshCubDb is still a work in progress.  Feel free to give it a go.
 | Read (sort)             | ✅     |
 | Read (calculations)     | ❌     |
 | Read (aggregates)       | ❌     |
-| Update                  | ❌     |
+| Update                  | ✅     |
 | Destroy                 | ❌     |
 
 ## Github Mirror
diff --git a/config/config.exs b/config/config.exs
index cf76d0a..5a5bc1b 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -10,4 +10,6 @@ config :git_ops,
 
 if Mix.env() in ~w[dev test]a do
   config :ash_cubdb, ash_apis: [Support.Api]
+
+  config :spark, :formatter, remove_parens?: true
 end
diff --git a/lib/ash_cub_db/data_layer.ex b/lib/ash_cub_db/data_layer.ex
index 53b1df8..54be159 100644
--- a/lib/ash_cub_db/data_layer.ex
+++ b/lib/ash_cub_db/data_layer.ex
@@ -14,6 +14,7 @@ defmodule AshCubDB.DataLayer do
     Changeset,
     Error,
     Error.Changes.InvalidAttribute,
+    Error.Changes.StaleRecord,
     Error.Invalid.TenantRequired,
     Filter.Runtime,
     Resource
@@ -50,6 +51,7 @@ defmodule AshCubDB.DataLayer do
   @doc false
   @impl true
   def can?(resource, :create), do: Dir.writable?(resource)
+  def can?(resource, :update), do: Dir.writable?(resource)
   def can?(resource, :upsert), do: Dir.writable?(resource)
   def can?(resource, :read), do: Dir.readable?(resource)
   def can?(_, :multitenancy), do: true
@@ -107,6 +109,22 @@ defmodule AshCubDB.DataLayer do
     end
   end
 
+  @doc false
+  @impl true
+  def update(resource, changeset) do
+    with :ok <- validate_tenant_configuration(resource, changeset.tenant),
+         {:ok, db} <- start(resource),
+         {:ok, record} <- Changeset.apply_attributes(changeset),
+         {:ok, key, data} <- Serde.serialise(record),
+         true <- CubDB.has_key?(db, key),
+         :ok <- CubDB.put(db, key, data) do
+      {:ok, set_loaded(record)}
+    else
+      false -> {:error, StaleRecord.exception(resource: resource)}
+      {:error, reason} -> {:error, Ash.Error.to_ash_error(reason)}
+    end
+  end
+
   @doc false
   @impl true
   def run_query(query, resource, parent \\ nil) do
diff --git a/test/ash_cub_db/data_layer_test.exs b/test/ash_cub_db/data_layer_test.exs
index d5837d2..5040a94 100644
--- a/test/ash_cub_db/data_layer_test.exs
+++ b/test/ash_cub_db/data_layer_test.exs
@@ -129,6 +129,21 @@ defmodule AshCubDB.DataLayerTest do
     end
   end
 
+  describe "update" do
+    test "records can be updated" do
+      post = insert!(Post)
+      params = Post |> params!() |> Map.take([:title])
+
+      assert {:ok, updated} = Post.update(post, params)
+      assert updated.id == post.id
+      assert updated.title == params.title
+
+      assert {:ok, updated} = Post.get(post.id)
+      assert updated.id == post.id
+      assert updated.title == params.title
+    end
+  end
+
   defp dump(resource) do
     resource
     |> via()
diff --git a/test/support/post.ex b/test/support/post.ex
index 7f65af5..ffac374 100644
--- a/test/support/post.ex
+++ b/test/support/post.ex
@@ -7,27 +7,29 @@ defmodule Support.Post do
   end
 
   attributes do
-    uuid_primary_key(:id) do
-      writable?(true)
+    uuid_primary_key :id do
+      writable? true
     end
 
-    attribute(:title, :string)
-    attribute(:body, :string)
+    attribute :title, :string
+    attribute :body, :string
   end
 
   actions do
     # defaults ~w[create read update destroy]a
-    defaults(~w[create read]a)
+    defaults ~w[create read update]a
   end
 
   relationships do
-    belongs_to(:author, Support.Author)
+    belongs_to :author, Support.Author
   end
 
   code_interface do
-    define_for(Support.Api)
+    define_for Support.Api
 
-    define(:create)
-    define(:read)
+    define :create
+    define :read
+    define :update
+    define :get, action: :read, get_by: [:id]
   end
 end