diff --git a/lib/architex/room_server.ex b/lib/architex/room_server.ex
index d32ae55..1119df6 100644
--- a/lib/architex/room_server.ex
+++ b/lib/architex/room_server.ex
@@ -21,7 +21,8 @@ defmodule Architex.RoomServer do
     Account,
     JoinedRoom,
     Device,
-    DeviceTransaction
+    DeviceTransaction,
+    Membership
   }
 
   alias Architex.StateResolution.Authorization
@@ -607,6 +608,7 @@ defmodule Architex.RoomServer do
       state_set = StateResolution.resolve_forward_extremities(event)
       # TODO: Do this as a background job, and not after every insert...
       _ = update_joined_rooms(room, state_set)
+      :ok = update_membership(room, state_set)
 
       {:ok, state_set, room, event}
     else
@@ -651,4 +653,34 @@ defmodule Architex.RoomServer do
         where: jr.room_id == ^room_id and a.localpart in ^not_joined_localparts
     )
   end
+
+  # TODO: Might be better to calculate membership changes...
+  @spec update_membership(Room.t(), t()) :: :ok
+  defp update_membership(%Room{id: room_id}, state_set) do
+    server_name = Architex.server_name()
+
+    state_set
+    |> Enum.filter(fn {{type, state_key}, _} ->
+      type == "m.room.member" and Architex.get_domain(state_key) == server_name
+    end)
+    |> Enum.group_by(
+      fn {_, %Event{content: %{"membership" => membership}}} ->
+        membership
+      end,
+      fn {{_, state_key}, _} ->
+        Architex.get_localpart(state_key)
+      end
+    )
+    |> Enum.each(fn {membership, localparts} ->
+      Repo.insert_all(
+        Membership,
+        from(a in Account,
+          where: a.localpart in ^localparts,
+          select: %{account_id: a.id, room_id: ^room_id, membership: ^membership}
+        ),
+        on_conflict: {:replace, [:membership]},
+        conflict_target: [:account_id, :room_id]
+      )
+    end)
+  end
 end
diff --git a/lib/architex/schema/membership.ex b/lib/architex/schema/membership.ex
new file mode 100644
index 0000000..0d24bf8
--- /dev/null
+++ b/lib/architex/schema/membership.ex
@@ -0,0 +1,18 @@
+defmodule Architex.Membership do
+  use Ecto.Schema
+
+  alias Architex.{Account, Room}
+
+  @type t :: %__MODULE__{
+          account_id: integer(),
+          room_id: String.t(),
+          membership: String.t()
+        }
+
+  @primary_key false
+  schema "membership" do
+    belongs_to :account, Account, primary_key: true
+    belongs_to :room, Room, primary_key: true, type: :string
+    field :membership, :string
+  end
+end
diff --git a/lib/architex_web/client/controllers/sync_controller.ex b/lib/architex_web/client/controllers/sync_controller.ex
index ce6d2c9..cb720bb 100644
--- a/lib/architex_web/client/controllers/sync_controller.ex
+++ b/lib/architex_web/client/controllers/sync_controller.ex
@@ -47,11 +47,12 @@ defmodule ArchitexWeb.Client.SyncController do
         {room_id, joined_room}
       end)
 
-    next_batch = Enum.map(events_per_room, fn {_, events} ->
-      %Event{nid: last_nid} = List.last(events)
-      last_nid
-    end)
-    |> Enum.max(fn -> 0 end)
+    next_batch =
+      Enum.map(events_per_room, fn {_, events} ->
+        %Event{nid: last_nid} = List.last(events)
+        last_nid
+      end)
+      |> Enum.max(fn -> 0 end)
 
     data = %{
       next_batch: Integer.to_string(next_batch),
diff --git a/priv/repo/migrations/20210830160818_create_initial_tables.exs b/priv/repo/migrations/20210830160818_create_initial_tables.exs
index 21b7fb2..f40b72a 100644
--- a/priv/repo/migrations/20210830160818_create_initial_tables.exs
+++ b/priv/repo/migrations/20210830160818_create_initial_tables.exs
@@ -91,5 +91,11 @@ defmodule Architex.Repo.Migrations.CreateInitialTables do
 
       add :event_id, :string, null: false
     end
+
+    create table(:membership, primary_key: false) do
+      add :account_id, references(:accounts), primary_key: true
+      add :room_id, references(:rooms, type: :string), primary_key: true
+      add :membership, :string, null: false
+    end
   end
 end