And Balances were backfilled unto the database.

Procfile

@@ -4,3 +4,4 @@ scheduler: bin/start-pgbouncer-stunnel mix exq.start scheduler
 blocks: bin/start-pgbouncer-stunnel mix scrape.blocks 1000000
 receipts: bin/start-pgbouncer-stunnel mix scrape.receipts 10000
 internal_transactions: bin/start-pgbouncer-stunnel mix scrape.internal_transactions 10000
+balances: bin/start-pgbouncer-stunnel mix scrape.balances 1000000

lib/explorer/skipped_balances.ex

@@ -0,0 +1,21 @@
+defmodule Explorer.SkippedBalances do
+  @moduledoc "Gets a list of Addresses that do not have balances."
+
+  alias Explorer.Address
+  alias Explorer.Repo
+
+  import Ecto.Query, only: [from: 2]
+
+  def fetch(count) do
+    query =
+      from(
+        address in Address,
+        select: address.hash,
+        where: is_nil(address.balance),
+        limit: ^count
+      )
+
+    query
+    |> Repo.all()
+  end
+end

lib/mix/tasks/scrape.balances.ex

@@ -0,0 +1,26 @@
+defmodule Mix.Tasks.Scrape.Balances do
+  @moduledoc "Populate Address balances."
+
+  use Mix.Task
+
+  alias Explorer.Repo
+  alias Explorer.SkippedBalances
+  alias Explorer.BalanceImporter
+
+  def run([]), do: run(1)
+
+  def run(count) do
+    [:postgrex, :ecto, :ethereumex, :tzdata]
+    |> Enum.each(&Application.ensure_all_started/1)
+
+    Repo.start_link()
+    Exq.start_link(mode: :enqueuer)
+
+    "#{count}"
+    |> String.to_integer()
+    |> SkippedBalances.fetch()
+    |> Flow.from_enumerable()
+    |> Flow.map(&BalanceImporter.import/1)
+    |> Enum.to_list()
+  end
+end

test/explorer/skipped_balances_test.exs

@@ -0,0 +1,18 @@
+defmodule Explorer.SkippedBalancesTest do
+  use Explorer.DataCase
+
+  alias Explorer.SkippedBalances
+
+  describe "fetch/1" do
+    test "returns a list of address hashes that do not have balances" do
+      insert(:address, hash: "0xcashews", balance: nil)
+      assert SkippedBalances.fetch(1) == ["0xcashews"]
+    end
+
+    test "only get a limited set of addresses" do
+      insert_list(10, :address, balance: nil)
+      insert_list(5, :address, balance: 55)
+      assert length(SkippedBalances.fetch(7)) == 7
+    end
+  end
+end