Don't expire idempotency cache for five minutes.

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -288,6 +288,8 @@ def post_status(%{assigns: %{user: user}} = conn, %{"status" => _} = params) do
         fallback: fn _ -> CommonAPI.post(user, params) end
       )
 
+    Cachex.expire(:user_cache, "idem:#{idempotency_key}", :timer.seconds(5 * 60))
+
     render(conn, StatusView, "status.json", %{activity: activity, for: user, as: :activity})
   end
 

test/web/mastodon_api/mastodon_api_controller_test.exs

@@ -75,6 +75,10 @@ test "posting a status", %{conn: conn} do
         "sensitive" => "false"
       })
 
+    {:ok, ttl} = Cachex.ttl(:user_cache, "idem:#{idempotency_key}")
+    # 5 Minutes
+    assert ttl > :timer.seconds(5 * 60 - 1)
+
     assert %{"content" => "cofe", "id" => id, "spoiler_text" => "2hu", "sensitive" => false} =
              json_response(conn_one, 200)