diff --git a/CHANGELOG.md b/CHANGELOG.md
index 141640ffdc..516e76ea98 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,16 +16,19 @@ All notable changes to this project will be documented in this file.
 - Add support for JSON logger, via LOG_FORMAT=json environment variable
 - Add support for 2FA authentication
 - Add 'browser_versions.csv' to CSV export
+- Add `CLICKHOUSE_MAX_BUFFER_SIZE_BYTES` env var which defaults to `100000` (100KB)
 
 ### Removed
 - Removed the nested custom event property breakdown UI when filtering by a goal in Goal Conversions
 - Removed the `prop-breakdown.csv` file from CSV export
+- Deprecated `CLICKHOUSE_MAX_BUFFER_SIZE`
 
 ### Changed
 - Limit the number of Goal Conversions shown on the dashboard and render a "Details" link when there are more entries to show
 - Show Outbound Links / File Downloads / 404 Pages / Cloaked Links instead of Goal Conversions when filtering by the corresponding goal
 - Require custom properties to be explicitly added from Site Settings > Custom Properties in order for them to show up on the dashboard
 - GA/SC sections moved to new settings: Integrations
+- Replace `CLICKHOUSE_MAX_BUFFER_SIZE` with `CLICKHOUSE_MAX_BUFFER_SIZE_BYTES`
 
 ### Fixed
 - Only return `(none)` values in custom property breakdown for the first page (pagination) of results
diff --git a/config/runtime.exs b/config/runtime.exs
index 27f1b54137..7339e64ec3 100644
--- a/config/runtime.exs
+++ b/config/runtime.exs
@@ -140,9 +140,15 @@ ch_db_url =
   |> get_var_from_path_or_env("CLICKHOUSE_FLUSH_INTERVAL_MS", "5000")
   |> Integer.parse()
 
+if get_var_from_path_or_env(config_dir, "CLICKHOUSE_MAX_BUFFER_SIZE") do
+  Logger.warning(
+    "CLICKHOUSE_MAX_BUFFER_SIZE is deprecated, please use CLICKHOUSE_MAX_BUFFER_SIZE_BYTES instead"
+  )
+end
+
 {ch_max_buffer_size, ""} =
   config_dir
-  |> get_var_from_path_or_env("CLICKHOUSE_MAX_BUFFER_SIZE", "10000")
+  |> get_var_from_path_or_env("CLICKHOUSE_MAX_BUFFER_SIZE_BYTES", "100000")
   |> Integer.parse()
 
 # Can be generated  with `Base.encode64(:crypto.strong_rand_bytes(32))` from
diff --git a/lib/plausible/application.ex b/lib/plausible/application.ex
index b9d58c3e5c..886993d12b 100644
--- a/lib/plausible/application.ex
+++ b/lib/plausible/application.ex
@@ -17,8 +17,8 @@ defmodule Plausible.Application do
       {Finch, name: Plausible.Finch, pools: finch_pool_config()},
       {Phoenix.PubSub, name: Plausible.PubSub},
       Plausible.Session.Salts,
-      Plausible.Event.WriteBuffer,
-      Plausible.Session.WriteBuffer,
+      Supervisor.child_spec(Plausible.Event.WriteBuffer, id: Plausible.Event.WriteBuffer),
+      Supervisor.child_spec(Plausible.Session.WriteBuffer, id: Plausible.Session.WriteBuffer),
       ReferrerBlocklist,
       Supervisor.child_spec({Cachex, name: :user_agents, limit: 10_000, stats: true},
         id: :cachex_user_agents
diff --git a/lib/plausible/event/write_buffer.ex b/lib/plausible/event/write_buffer.ex
index 37a9cd39b0..3966b5a3f7 100644
--- a/lib/plausible/event/write_buffer.ex
+++ b/lib/plausible/event/write_buffer.ex
@@ -1,79 +1,38 @@
 defmodule Plausible.Event.WriteBuffer do
-  use GenServer
-  require Logger
+  @moduledoc false
 
-  alias Plausible.IngestRepo
+  %{
+    header: header,
+    insert_sql: insert_sql,
+    insert_opts: insert_opts,
+    fields: fields,
+    encoding_types: encoding_types
+  } =
+    Plausible.Ingestion.WriteBuffer.compile_time_prepare(Plausible.ClickhouseEventV2)
 
-  def start_link(_opts) do
-    GenServer.start_link(__MODULE__, [], name: __MODULE__)
-  end
+  def child_spec(opts) do
+    opts =
+      Keyword.merge(opts,
+        name: __MODULE__,
+        header: unquote(header),
+        insert_sql: unquote(insert_sql),
+        insert_opts: unquote(insert_opts)
+      )
 
-  def init(buffer) do
-    Process.flag(:trap_exit, true)
-    timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:ok, %{buffer: buffer, timer: timer}}
+    Plausible.Ingestion.WriteBuffer.child_spec(opts)
   end
 
   def insert(event) do
-    GenServer.cast(__MODULE__, {:insert, event})
+    row_binary =
+      [Enum.map(unquote(fields), fn field -> Map.fetch!(event, field) end)]
+      |> Ch.RowBinary._encode_rows(unquote(encoding_types))
+      |> IO.iodata_to_binary()
+
+    :ok = Plausible.Ingestion.WriteBuffer.insert(__MODULE__, row_binary)
     {:ok, event}
   end
 
-  def flush() do
-    GenServer.call(__MODULE__, :flush, :infinity)
-    :ok
-  end
-
-  def handle_cast({:insert, event}, %{buffer: buffer} = state) do
-    new_buffer = [event | buffer]
-
-    if length(new_buffer) >= max_buffer_size() do
-      Logger.info("Buffer full, flushing to disk")
-      Process.cancel_timer(state[:timer])
-      do_flush(new_buffer)
-      new_timer = Process.send_after(self(), :tick, flush_interval_ms())
-      {:noreply, %{buffer: [], timer: new_timer}}
-    else
-      {:noreply, %{state | buffer: new_buffer}}
-    end
-  end
-
-  def handle_info(:tick, %{buffer: buffer}) do
-    do_flush(buffer)
-    timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:noreply, %{buffer: [], timer: timer}}
-  end
-
-  def handle_call(:flush, _from, %{buffer: buffer} = state) do
-    Process.cancel_timer(state[:timer])
-    do_flush(buffer)
-    new_timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:reply, nil, %{buffer: [], timer: new_timer}}
-  end
-
-  def terminate(_reason, %{buffer: buffer}) do
-    Logger.info("Flushing event buffer before shutdown...")
-    do_flush(buffer)
-  end
-
-  defp do_flush(buffer) do
-    case buffer do
-      [] ->
-        nil
-
-      events ->
-        Logger.info("Flushing #{length(events)} events")
-        events = Enum.map(events, &(Map.from_struct(&1) |> Map.delete(:__meta__)))
-
-        IngestRepo.insert_all(Plausible.ClickhouseEventV2, events)
-    end
-  end
-
-  defp flush_interval_ms() do
-    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :flush_interval_ms)
-  end
-
-  defp max_buffer_size() do
-    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :max_buffer_size)
+  def flush do
+    Plausible.Ingestion.WriteBuffer.flush(__MODULE__)
   end
 end
diff --git a/lib/plausible/ingestion/write_buffer.ex b/lib/plausible/ingestion/write_buffer.ex
new file mode 100644
index 0000000000..e62580cd5b
--- /dev/null
+++ b/lib/plausible/ingestion/write_buffer.ex
@@ -0,0 +1,149 @@
+defmodule Plausible.Ingestion.WriteBuffer do
+  @moduledoc false
+  use GenServer
+  require Logger
+
+  alias Plausible.IngestRepo
+
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: Keyword.fetch!(opts, :name))
+  end
+
+  def insert(server, row_binary) do
+    GenServer.cast(server, {:insert, row_binary})
+  end
+
+  def flush(server) do
+    GenServer.call(server, :flush, :infinity)
+  end
+
+  @impl true
+  def init(opts) do
+    buffer = opts[:buffer] || []
+    max_buffer_size = opts[:max_buffer_size] || default_max_buffer_size()
+    flush_interval_ms = opts[:flush_interval_ms] || default_flush_interval_ms()
+
+    Process.flag(:trap_exit, true)
+    timer = Process.send_after(self(), :tick, flush_interval_ms)
+
+    {:ok,
+     %{
+       buffer: buffer,
+       timer: timer,
+       name: Keyword.fetch!(opts, :name),
+       insert_sql: Keyword.fetch!(opts, :insert_sql),
+       insert_opts: Keyword.fetch!(opts, :insert_opts),
+       header: Keyword.fetch!(opts, :header),
+       buffer_size: IO.iodata_length(buffer),
+       max_buffer_size: max_buffer_size,
+       flush_interval_ms: flush_interval_ms
+     }}
+  end
+
+  @impl true
+  def handle_cast({:insert, row_binary}, state) do
+    state = %{
+      state
+      | buffer: [state.buffer | row_binary],
+        buffer_size: state.buffer_size + IO.iodata_length(row_binary)
+    }
+
+    if state.buffer_size >= state.max_buffer_size do
+      Logger.info("#{state.name} buffer full, flushing to ClickHouse")
+      Process.cancel_timer(state.timer)
+      do_flush(state)
+      new_timer = Process.send_after(self(), :tick, state.flush_interval_ms)
+      {:noreply, %{state | buffer: [], timer: new_timer, buffer_size: 0}}
+    else
+      {:noreply, state}
+    end
+  end
+
+  @impl true
+  def handle_info(:tick, state) do
+    do_flush(state)
+    timer = Process.send_after(self(), :tick, state.flush_interval_ms)
+    {:noreply, %{state | buffer: [], buffer_size: 0, timer: timer}}
+  end
+
+  @impl true
+  def handle_call(:flush, _from, state) do
+    %{timer: timer, flush_interval_ms: flush_interval_ms} = state
+    Process.cancel_timer(timer)
+    do_flush(state)
+    new_timer = Process.send_after(self(), :tick, flush_interval_ms)
+    {:reply, :ok, %{state | buffer: [], buffer_size: 0, timer: new_timer}}
+  end
+
+  @impl true
+  def terminate(_reason, %{name: name} = state) do
+    Logger.info("Flushing #{name} buffer before shutdown...")
+    do_flush(state)
+  end
+
+  defp do_flush(state) do
+    %{
+      buffer: buffer,
+      buffer_size: buffer_size,
+      insert_opts: insert_opts,
+      insert_sql: insert_sql,
+      header: header,
+      name: name
+    } = state
+
+    case buffer do
+      [] ->
+        nil
+
+      _not_empty ->
+        Logger.info("Flushing #{buffer_size} byte(s) RowBinary from #{name}")
+        IngestRepo.query!(insert_sql, [header | buffer], insert_opts)
+    end
+  end
+
+  defp default_flush_interval_ms do
+    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :flush_interval_ms)
+  end
+
+  defp default_max_buffer_size do
+    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :max_buffer_size)
+  end
+
+  @doc false
+  def compile_time_prepare(schema) do
+    fields = schema.__schema__(:fields)
+
+    types =
+      Enum.map(fields, fn field ->
+        type = schema.__schema__(:type, field) || raise "missing type for #{field}"
+
+        type
+        |> Ecto.Type.type()
+        |> Ecto.Adapters.ClickHouse.Schema.remap_type(schema, field)
+      end)
+
+    encoding_types = Ch.RowBinary.encoding_types(types)
+
+    header =
+      fields
+      |> Enum.map(&to_string/1)
+      |> Ch.RowBinary.encode_names_and_types(types)
+      |> IO.iodata_to_binary()
+
+    insert_sql = "INSERT INTO #{schema.__schema__(:source)} FORMAT RowBinaryWithNamesAndTypes"
+
+    %{
+      fields: fields,
+      types: types,
+      encoding_types: encoding_types,
+      header: header,
+      insert_sql: insert_sql,
+      insert_opts: [
+        command: :insert,
+        encode: false,
+        source: schema.__schema__(:source),
+        cast_params: []
+      ]
+    }
+  end
+end
diff --git a/lib/plausible/session/cache_store.ex b/lib/plausible/session/cache_store.ex
index 3350936ffa..b2eeffc1bc 100644
--- a/lib/plausible/session/cache_store.ex
+++ b/lib/plausible/session/cache_store.ex
@@ -8,7 +8,7 @@ defmodule Plausible.Session.CacheStore do
     session =
       if found_session do
         updated_session = update_session(found_session, event)
-        buffer.insert([%{updated_session | sign: 1}, %{found_session | sign: -1}])
+        buffer.insert([%{found_session | sign: -1}, %{updated_session | sign: 1}])
         persist_session(updated_session)
       else
         new_session = new_session_from_event(event)
diff --git a/lib/plausible/session/write_buffer.ex b/lib/plausible/session/write_buffer.ex
index 770fc965c1..1adcbbb67d 100644
--- a/lib/plausible/session/write_buffer.ex
+++ b/lib/plausible/session/write_buffer.ex
@@ -1,83 +1,43 @@
 defmodule Plausible.Session.WriteBuffer do
-  use GenServer
-  require Logger
+  @moduledoc false
 
-  alias Plausible.IngestRepo
+  %{
+    header: header,
+    insert_sql: insert_sql,
+    insert_opts: insert_opts,
+    fields: fields,
+    encoding_types: encoding_types
+  } =
+    Plausible.Ingestion.WriteBuffer.compile_time_prepare(Plausible.ClickhouseSessionV2)
 
-  def start_link(_opts) do
-    GenServer.start_link(__MODULE__, [], name: __MODULE__)
-  end
+  def child_spec(opts) do
+    opts =
+      Keyword.merge(opts,
+        name: __MODULE__,
+        header: unquote(header),
+        insert_sql: unquote(insert_sql),
+        insert_opts: unquote(insert_opts)
+      )
 
-  def init(buffer) do
-    Process.flag(:trap_exit, true)
-    timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:ok, %{buffer: buffer, timer: timer}}
+    Plausible.Ingestion.WriteBuffer.child_spec(opts)
   end
 
   def insert(sessions) do
-    GenServer.cast(__MODULE__, {:insert, sessions})
+    row_binary =
+      sessions
+      |> Enum.map(fn %{is_bounce: is_bounce} = session ->
+        {:ok, is_bounce} = Plausible.ClickhouseSessionV2.BoolUInt8.dump(is_bounce)
+        session = %{session | is_bounce: is_bounce}
+        Enum.map(unquote(fields), fn field -> Map.fetch!(session, field) end)
+      end)
+      |> Ch.RowBinary._encode_rows(unquote(encoding_types))
+      |> IO.iodata_to_binary()
+
+    :ok = Plausible.Ingestion.WriteBuffer.insert(__MODULE__, row_binary)
     {:ok, sessions}
   end
 
-  def flush() do
-    GenServer.call(__MODULE__, :flush, :infinity)
-    :ok
-  end
-
-  def handle_cast({:insert, sessions}, %{buffer: buffer} = state) do
-    new_buffer = sessions ++ buffer
-
-    if length(new_buffer) >= max_buffer_size() do
-      Logger.info("Buffer full, flushing to disk")
-      Process.cancel_timer(state[:timer])
-      do_flush(new_buffer)
-      new_timer = Process.send_after(self(), :tick, flush_interval_ms())
-      {:noreply, %{buffer: [], timer: new_timer}}
-    else
-      {:noreply, %{state | buffer: new_buffer}}
-    end
-  end
-
-  def handle_info(:tick, %{buffer: buffer}) do
-    do_flush(buffer)
-    timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:noreply, %{buffer: [], timer: timer}}
-  end
-
-  def handle_call(:flush, _from, %{buffer: buffer} = state) do
-    Process.cancel_timer(state[:timer])
-    do_flush(buffer)
-    new_timer = Process.send_after(self(), :tick, flush_interval_ms())
-    {:reply, nil, %{buffer: [], timer: new_timer}}
-  end
-
-  def terminate(_reason, %{buffer: buffer}) do
-    Logger.info("Flushing session buffer before shutdown...")
-    do_flush(buffer)
-  end
-
-  defp do_flush(buffer) do
-    case buffer do
-      [] ->
-        nil
-
-      sessions ->
-        Logger.info("Flushing #{length(sessions)} sessions")
-
-        sessions =
-          sessions
-          |> Enum.map(&(Map.from_struct(&1) |> Map.delete(:__meta__)))
-          |> Enum.reverse()
-
-        IngestRepo.insert_all(Plausible.ClickhouseSessionV2, sessions)
-    end
-  end
-
-  defp flush_interval_ms() do
-    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :flush_interval_ms)
-  end
-
-  defp max_buffer_size() do
-    Keyword.fetch!(Application.get_env(:plausible, IngestRepo), :max_buffer_size)
+  def flush do
+    Plausible.Ingestion.WriteBuffer.flush(__MODULE__)
   end
 end
diff --git a/test/plausible/session/cache_store_test.exs b/test/plausible/session/cache_store_test.exs
index aa4a43798f..555aedd37d 100644
--- a/test/plausible/session/cache_store_test.exs
+++ b/test/plausible/session/cache_store_test.exs
@@ -88,7 +88,7 @@ defmodule Plausible.Session.CacheStoreTest do
 
     CacheStore.on_event(event1, nil, buffer)
     CacheStore.on_event(event2, nil, buffer)
-    assert_receive({WriteBuffer, :insert, [[session, _negative_record]]})
+    assert_receive({WriteBuffer, :insert, [[_negative_record, session]]})
     assert session.is_bounce == false
     assert session.duration == 10
     assert session.pageviews == 2
@@ -113,7 +113,7 @@ defmodule Plausible.Session.CacheStoreTest do
     CacheStore.on_event(event1, nil, buffer)
     CacheStore.on_event(event2, nil, buffer)
 
-    assert_receive({WriteBuffer, :insert, [[session, _negative_record]]})
+    assert_receive({WriteBuffer, :insert, [[_negative_record, session]]})
     assert session.duration == 10
   end