diff --git a/assets/js/contacts_map_hook.ts b/assets/js/contacts_map_hook.ts
index efeec48d..0e36ea2e 100644
--- a/assets/js/contacts_map_hook.ts
+++ b/assets/js/contacts_map_hook.ts
@@ -51,7 +51,11 @@ function bandColor(band: number): string {
 
 export const ContactsMap = {
   mounted(this: ContactsMapHook) {
-    this.allContacts = JSON.parse(this.el.dataset.contacts!)
+    // Contacts payload (~5 MB) comes from a standalone HTTP endpoint that
+    // serves pre-gzipped JSON. This keeps it out of the initial HTML and
+    // lets the browser cache it independently of the LiveView.
+    const fetchUrl = this.el.dataset.fetchUrl || "/api/contacts/map"
+    this.allContacts = []
     this.callsignFilter = ""
     this.enabledBands = new Set()
     this.lineLayer = L.layerGroup()
@@ -66,6 +70,23 @@ export const ContactsMap = {
 
     // Defer map init until container has dimensions
     requestAnimationFrame(() => this.initMap())
+
+    // Fetch contacts in parallel with map init. Once both are done,
+    // `rebuildMap()` draws everything. Starts earlier than a LiveView
+    // push_event because the HTTP request doesn't wait for the socket
+    // handshake.
+    // No explicit Accept header — the :browser pipeline's `plug :accepts`
+    // only whitelists "html", so setting accept: application/json triggers
+    // a 406. The default `*/*` matches fine and we still parse the body
+    // as JSON ourselves.
+    fetch(fetchUrl)
+      .then(resp => resp.json())
+      .then(contacts => {
+        this.allContacts = contacts
+        for (const c of contacts) this.enabledBands.add(c[4])
+        if (this.map) this.rebuildMap()
+      })
+      .catch(err => console.error("Failed to load contacts:", err))
   },
 
   initMap(this: ContactsMapHook) {
@@ -85,10 +106,11 @@ export const ContactsMap = {
     this.lineLayer.addTo(this.map)
     this.dotLayer.addTo(this.map)
 
-    // Enable all bands initially
-    for (const c of this.allContacts) this.enabledBands.add(c[4])
-
-    this.rebuildMap()
+    // If contacts arrived before the map was ready, draw them now.
+    if (this.allContacts.length > 0) {
+      for (const c of this.allContacts) this.enabledBands.add(c[4])
+      this.rebuildMap()
+    }
   },
 
   rebuildMap(this: ContactsMapHook) {
diff --git a/lib/microwaveprop/radio.ex b/lib/microwaveprop/radio.ex
index 77663f7a..eb7a9f99 100644
--- a/lib/microwaveprop/radio.ex
+++ b/lib/microwaveprop/radio.ex
@@ -538,6 +538,7 @@ defmodule Microwaveprop.Radio do
         with {:ok, _} <- result do
           Cache.invalidate(@count_cache_key)
           Cache.invalidate(@map_payload_cache_key)
+          Cache.invalidate({MicrowavepropWeb.ContactMapController, :gzipped_payload})
         end
 
         result
diff --git a/lib/microwaveprop_web/controllers/contact_map_controller.ex b/lib/microwaveprop_web/controllers/contact_map_controller.ex
new file mode 100644
index 00000000..8a22eb9c
--- /dev/null
+++ b/lib/microwaveprop_web/controllers/contact_map_controller.ex
@@ -0,0 +1,53 @@
+defmodule MicrowavepropWeb.ContactMapController do
+  @moduledoc """
+  Serves the contact map JSON payload as a standalone HTTP endpoint. Keeps
+  the ~5 MB blob out of the `/contacts/map` LiveView's initial HTML response
+  and lets the browser's native `Content-Encoding: gzip` handling do the
+  compression. The payload itself is served from `Microwaveprop.Cache` via
+  `Radio.contact_map_payload/0`.
+  """
+  use MicrowavepropWeb, :controller
+
+  alias Microwaveprop.Cache
+  alias Microwaveprop.Radio
+
+  @cache_key {__MODULE__, :gzipped_payload}
+  @cache_ttl_ms 10 * 60 * 1_000
+
+  @spec show(Plug.Conn.t(), map()) :: Plug.Conn.t()
+  def show(conn, _params) do
+    {body, encoding} = gzipped_or_plain_body(conn)
+
+    conn
+    |> put_resp_content_type("application/json")
+    |> maybe_put_encoding(encoding)
+    |> put_resp_header("cache-control", "public, max-age=60")
+    |> send_resp(200, body)
+  end
+
+  defp gzipped_or_plain_body(conn) do
+    if accepts_gzip?(conn) do
+      {gzipped_payload(), :gzip}
+    else
+      %{json: iodata} = Radio.contact_map_payload()
+      {IO.iodata_to_binary(iodata), :identity}
+    end
+  end
+
+  defp gzipped_payload do
+    Cache.fetch_or_store(@cache_key, @cache_ttl_ms, fn ->
+      %{json: iodata} = Radio.contact_map_payload()
+      :zlib.gzip(IO.iodata_to_binary(iodata))
+    end)
+  end
+
+  defp accepts_gzip?(conn) do
+    case get_req_header(conn, "accept-encoding") do
+      [value | _] -> String.contains?(value, "gzip")
+      _ -> false
+    end
+  end
+
+  defp maybe_put_encoding(conn, :gzip), do: put_resp_header(conn, "content-encoding", "gzip")
+  defp maybe_put_encoding(conn, :identity), do: conn
+end
diff --git a/lib/microwaveprop_web/live/contact_live/show.ex b/lib/microwaveprop_web/live/contact_live/show.ex
index 6b880a80..7c3f0926 100644
--- a/lib/microwaveprop_web/live/contact_live/show.ex
+++ b/lib/microwaveprop_web/live/contact_live/show.ex
@@ -229,18 +229,22 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   def handle_info({:hydrate, can_enqueue}, socket) do
     contact = socket.assigns.contact
 
-    weather = load_weather(contact)
-    solar = if can_enqueue, do: maybe_enqueue_solar(contact), else: load_solar(contact)
-    hrrr_path = Weather.hrrr_profiles_for_path(contact)
+    # Five independent DB loads run in parallel — total latency drops from
+    # sum(each) to max(each). The heaviest is `hrrr_profiles_for_path`
+    # against the 42M-row partitioned table.
+    %{
+      weather: weather,
+      solar: solar,
+      hrrr_path: hrrr_path,
+      terrain: terrain,
+      iemre: iemre
+    } = parallel_hydrate(contact, can_enqueue)
+
     hrrr = List.first(hrrr_path)
-
-    {hrrr, contact} =
-      if can_enqueue, do: maybe_enqueue_hrrr(hrrr, contact), else: {hrrr, contact}
-
-    terrain = Terrain.get_terrain_profile(contact.id)
+    {hrrr, contact} = if can_enqueue, do: maybe_enqueue_hrrr(hrrr, contact), else: {hrrr, contact}
     contact = if can_enqueue, do: maybe_enqueue_terrain(terrain, contact), else: contact
     contact = if can_enqueue, do: maybe_enqueue_weather(weather, contact), else: contact
-    iemre = load_iemre(contact)
+
     elevation_profile = compute_elevation_profile(contact, hrrr_path, weather.soundings)
 
     propagation_analysis =
@@ -397,6 +401,21 @@ defmodule MicrowavepropWeb.ContactLive.Show do
   defp sounding_sort_key("lifted_index"), do: &(&1.lifted_index || 0)
   defp sounding_sort_key(_), do: fn s -> s.station.name || s.station.station_code end
 
+  defp parallel_hydrate(contact, can_enqueue) do
+    tasks = %{
+      weather: Task.async(fn -> load_weather(contact) end),
+      solar:
+        Task.async(fn ->
+          if can_enqueue, do: maybe_enqueue_solar(contact), else: load_solar(contact)
+        end),
+      hrrr_path: Task.async(fn -> Weather.hrrr_profiles_for_path(contact) end),
+      terrain: Task.async(fn -> Terrain.get_terrain_profile(contact.id) end),
+      iemre: Task.async(fn -> load_iemre(contact) end)
+    }
+
+    Map.new(tasks, fn {key, task} -> {key, Task.await(task, 30_000)} end)
+  end
+
   defp load_iemre(contact) do
     case Weather.iemre_for_contact(contact) do
       %{hourly: hourly} = obs when is_list(hourly) and hourly != [] ->
diff --git a/lib/microwaveprop_web/live/contact_map_live.ex b/lib/microwaveprop_web/live/contact_map_live.ex
index 26ee2a11..6250d8ff 100644
--- a/lib/microwaveprop_web/live/contact_map_live.ex
+++ b/lib/microwaveprop_web/live/contact_map_live.ex
@@ -21,12 +21,16 @@ defmodule MicrowavepropWeb.ContactMapLive do
 
   @impl true
   def mount(_params, _session, socket) do
-    %{json: json, count: count, bands: bands} = Radio.contact_map_payload()
+    # Shell renders immediately with filter chrome (count + bands list). The
+    # JS hook fetches the ~5 MB contacts payload from `/api/contacts/map`
+    # after mount, which streams it as pre-gzipped bytes via the browser's
+    # native `Content-Encoding: gzip` handling. This gets the heavy payload
+    # off the initial HTML entirely.
+    %{count: count, bands: bands} = Radio.contact_map_payload()
 
     {:ok,
      assign(socket,
        page_title: "Contact Map",
-       contacts_json: IO.iodata_to_binary(json),
        contact_count: count,
        all_bands: bands,
        enabled_bands: MapSet.new(bands),
@@ -91,8 +95,8 @@ defmodule MicrowavepropWeb.ContactMapLive do
           id="contacts-map"
           phx-hook="ContactsMap"
           phx-update="ignore"
+          data-fetch-url="/api/contacts/map"
           class="absolute inset-0 z-0"
-          data-contacts={@contacts_json}
         >
         </div>
 
diff --git a/lib/microwaveprop_web/router.ex b/lib/microwaveprop_web/router.ex
index 71aaf28c..fad9442f 100644
--- a/lib/microwaveprop_web/router.ex
+++ b/lib/microwaveprop_web/router.ex
@@ -66,6 +66,7 @@ defmodule MicrowavepropWeb.Router do
     pipe_through :browser
 
     get "/", PageController, :home
+    get "/api/contacts/map", ContactMapController, :show
 
     live_session :public, on_mount: [{MicrowavepropWeb.UserAuth, :default}] do
       live "/submit", SubmitLive