diff --git a/lib/plexus/apps.ex b/lib/plexus/apps.ex
index c55f6c52..638d3be7 100644
--- a/lib/plexus/apps.ex
+++ b/lib/plexus/apps.ex
@@ -50,6 +50,14 @@ defmodule Plexus.Apps do
     |> Repo.one!()
   end
 
+  @spec fetch_app(String.t()) :: {:ok, App.t()} | {:error, :not_found}
+  def fetch_app(package) do
+    case Repo.get(App, package) do
+      %App{} = app -> {:ok, app}
+      nil -> {:error, :not_found}
+    end
+  end
+
   @spec create_app(%{
           optional(:icon_url) => String.t(),
           package: String.t(),
@@ -63,8 +71,9 @@ defmodule Plexus.Apps do
   end
 
   @spec update_app(App.t(), %{
+          optional(:updated_at) => DateTime.t(),
           optional(:icon_url) => String.t(),
-          name: String.t()
+          optional(:name) => String.t()
         }) :: {:ok, App.t()} | {:error, Ecto.Changeset.t()}
   def update_app(%App{} = app, params) do
     app
@@ -126,6 +135,9 @@ defmodule Plexus.Apps do
       {_, ""}, query ->
         query
 
+      {:updated_at_greater_than_or_equal_to, dt}, query ->
+        from q in query, where: q.updated_at >= ^dt
+
       {:search_term, search_term}, query ->
         pattern = "%#{search_term}%"
 
diff --git a/lib/plexus/ratings.ex b/lib/plexus/ratings.ex
index 5ea73c6b..97f66a2d 100644
--- a/lib/plexus/ratings.ex
+++ b/lib/plexus/ratings.ex
@@ -4,6 +4,7 @@ defmodule Plexus.Ratings do
   """
   import Ecto.Query
 
+  alias Plexus.Apps
   alias Plexus.PaginationHelpers
   alias Plexus.QueryHelpers
   alias Plexus.Repo
@@ -55,11 +56,14 @@ defmodule Plexus.Ratings do
           installation_source: String.t(),
           rating_type: atom(),
           score: pos_integer()
-        }) :: {:ok, Rating.t()} | {:error, Ecto.Changeset.t()}
-  def create_rating(params) do
-    %Rating{}
-    |> Rating.changeset(params)
-    |> Repo.insert()
+        }) :: {:ok, Rating.t()} | {:error, :not_found} | {:error, Ecto.Changeset.t()}
+  def create_rating(%{app_package: app_package} = params) do
+    Repo.transact(fn ->
+      with {:ok, app} <- Apps.fetch_app(app_package),
+           {:ok, _app} <- Apps.update_app(app, %{updated_at: DateTime.utc_now()}) do
+        Repo.insert(Rating.changeset(%Rating{}, params))
+      end
+    end)
     |> broadcast(:app_rating_updated)
   end
 
diff --git a/lib/plexus/schemas/app.ex b/lib/plexus/schemas/app.ex
index ee096569..bf7c4300 100644
--- a/lib/plexus/schemas/app.ex
+++ b/lib/plexus/schemas/app.ex
@@ -20,7 +20,7 @@ defmodule Plexus.Schemas.App do
   @spec changeset(App.t(), map()) :: Ecto.Changeset.t()
   def changeset(%App{} = app, params) do
     app
-    |> cast(params, [:package, :name, :icon_url])
+    |> cast(params, [:package, :name, :icon_url, :updated_at])
     |> validate_required([:package, :name])
     |> unique_constraint(:package, name: :apps_pkey)
   end
diff --git a/lib/plexus_web/controllers/api/v1/app_controller.ex b/lib/plexus_web/controllers/api/v1/app_controller.ex
index 70f3b140..89a5e435 100644
--- a/lib/plexus_web/controllers/api/v1/app_controller.ex
+++ b/lib/plexus_web/controllers/api/v1/app_controller.ex
@@ -17,7 +17,17 @@ defmodule PlexusWeb.API.V1.AppController do
       page: [in: :query, description: "Page number", type: :integer, example: 1],
       limit: [in: :query, description: "Max results per page", type: :integer, example: 25],
       scores: [in: :query, description: "Include scores", type: :boolean, example: true],
-      q: [in: :query, description: "Search query", type: :string, example: "Signal"]
+      q: [in: :query, description: "Search query", type: :string, example: "Signal"],
+      last_updated: [
+        in: :query,
+        description: "Apps that have updates after or on your datetime. Using RFC 3339",
+        type: %OpenApiSpex.Schema{type: :string, format: "date-time"},
+        example:
+          DateTime.utc_now()
+          |> DateTime.add(-7, :day)
+          |> DateTime.truncate(:second)
+          |> DateTime.to_iso8601(:extended)
+      ]
     ],
     responses: [
       ok: {"Applications", "application/json", AppsResponse}
@@ -77,6 +87,15 @@ defmodule PlexusWeb.API.V1.AppController do
       {"scores", "true"}, acc ->
         Keyword.put(acc, :scores, true)
 
+      {"last_updated", last_updated}, acc ->
+        case DateTime.from_iso8601(last_updated) do
+          {:ok, last_updated_dt, _utc_offset} ->
+            Keyword.put(acc, :updated_at_greater_than_or_equal_to, last_updated_dt)
+
+          _ ->
+            acc
+        end
+
       {"page", page}, acc ->
         case Integer.parse(page) do
           {value, _remainder} ->
diff --git a/lib/plexus_web/controllers/api/v1/app_json.ex b/lib/plexus_web/controllers/api/v1/app_json.ex
index 290c079c..b964387e 100644
--- a/lib/plexus_web/controllers/api/v1/app_json.ex
+++ b/lib/plexus_web/controllers/api/v1/app_json.ex
@@ -19,7 +19,8 @@ defmodule PlexusWeb.API.V1.AppJSON do
     %{
       package: app.package,
       name: app.name,
-      icon_url: app.icon_url
+      icon_url: app.icon_url,
+      updated_at: DateTime.truncate(app.updated_at, :second)
     }
     |> merge_scores(app.scores)
   end
diff --git a/lib/plexus_web/controllers/api/v1/schemas/app.ex b/lib/plexus_web/controllers/api/v1/schemas/app.ex
index 8cbfb146..5e900681 100644
--- a/lib/plexus_web/controllers/api/v1/schemas/app.ex
+++ b/lib/plexus_web/controllers/api/v1/schemas/app.ex
@@ -16,6 +16,7 @@ defmodule PlexusWeb.API.V1.Schemas.App do
     example: %{
       "name" => "Signal",
       "package" => "org.thoughtcrime.securesms",
+      "updated_at" => "2024-04-30T22:41:19Z",
       "scores" => %{
         "native" => %{
           "rating_type" => "native",
diff --git a/lib/plexus_web/controllers/api/v1/schemas/app_response.ex b/lib/plexus_web/controllers/api/v1/schemas/app_response.ex
index 07164c61..c0aefbdc 100644
--- a/lib/plexus_web/controllers/api/v1/schemas/app_response.ex
+++ b/lib/plexus_web/controllers/api/v1/schemas/app_response.ex
@@ -14,6 +14,7 @@ defmodule PlexusWeb.API.V1.Schemas.AppResponse do
         %{
           "name" => "Signal",
           "package" => "org.thoughtcrime.securesms",
+          "updated_at" => "2024-04-30T22:41:19Z",
           "scores" => %{
             "native" => %{
               "rating_type" => "native",
diff --git a/lib/plexus_web/controllers/api/v1/schemas/apps_response.ex b/lib/plexus_web/controllers/api/v1/schemas/apps_response.ex
index 6e6777f2..b943b09b 100644
--- a/lib/plexus_web/controllers/api/v1/schemas/apps_response.ex
+++ b/lib/plexus_web/controllers/api/v1/schemas/apps_response.ex
@@ -17,6 +17,7 @@ defmodule PlexusWeb.API.V1.Schemas.AppsResponse do
         %{
           "name" => "Signal",
           "package" => "org.thoughtcrime.securesms",
+          "updated_at" => "2024-04-30T22:41:19Z",
           "scores" => %{
             "native" => %{
               "rating_type" => "native",
diff --git a/test/plexus/ratings_test.exs b/test/plexus/ratings_test.exs
index 54555332..74046653 100644
--- a/test/plexus/ratings_test.exs
+++ b/test/plexus/ratings_test.exs
@@ -8,7 +8,7 @@ defmodule Plexus.RatingsTest do
   alias Plexus.Schemas.Rating
 
   @invalid_attrs %{
-    app_package: nil,
+    app_package: "",
     app_build_number: nil,
     app_version: nil,
     rating_type: nil,
@@ -65,7 +65,7 @@ defmodule Plexus.RatingsTest do
     end
 
     test "invalid data returns error changeset" do
-      assert {:error, %Ecto.Changeset{}} = Ratings.create_rating(@invalid_attrs)
+      assert {:error, _reason} = Ratings.create_rating(@invalid_attrs)
     end
   end
 end