diff --git a/tensorstore/internal/BUILD b/tensorstore/internal/BUILD
index bf5e8250e..8d23b104d 100644
--- a/tensorstore/internal/BUILD
+++ b/tensorstore/internal/BUILD
@@ -146,12 +146,12 @@ tensorstore_cc_library(
         "concurrency_resource_provider.h",
     ],
     deps = [
-        ":thread_pool",
         ":type_traits",
         "//tensorstore:context",
         "//tensorstore/internal/cache_key",
         "//tensorstore/internal/json_binding",
         "//tensorstore/internal/json_binding:bindable",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/util:executor",
         "//tensorstore/util:result",
         "@com_github_nlohmann_json//:nlohmann_json",
@@ -166,7 +166,7 @@ tensorstore_cc_library(
     hdrs = ["concurrent_testutil.h"],
     deps = [
         ":multi_barrier",
-        ":thread",
+        "//tensorstore/internal/thread",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/log:absl_log",
     ],
@@ -1742,68 +1742,6 @@ tensorstore_cc_library(
     ],
 )
 
-tensorstore_cc_library(
-    name = "thread",
-    srcs = ["thread.cc"],
-    hdrs = ["thread.h"],
-    deps = [
-        "@com_google_absl//absl/functional:any_invocable",
-        "@com_google_absl//absl/log:absl_check",
-    ],
-)
-
-tensorstore_cc_test(
-    name = "thread_test",
-    srcs = ["thread_test.cc"],
-    deps = [
-        ":thread",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
-tensorstore_cc_library(
-    name = "thread_pool",
-    srcs = ["thread_pool.cc"],
-    hdrs = ["thread_pool.h"],
-    deps = [
-        ":attributes",
-        ":intrusive_ptr",
-        ":mutex",
-        ":no_destructor",
-        ":thread",
-        "//tensorstore/internal/metrics",
-        "//tensorstore/internal/tracing",
-        "//tensorstore/util:executor",
-        "@com_google_absl//absl/base:core_headers",
-        "@com_google_absl//absl/functional:any_invocable",
-        "@com_google_absl//absl/log:absl_check",
-        "@com_google_absl//absl/strings",
-        "@com_google_absl//absl/synchronization",
-        "@com_google_absl//absl/time",
-    ],
-)
-
-tensorstore_cc_test(
-    name = "thread_pool_test",
-    size = "small",
-    deps = [
-        ":thread_pool",
-        ":thread_pool_test_lib",
-    ],
-)
-
-tensorstore_cc_library(
-    name = "thread_pool_test_lib",
-    testonly = True,
-    srcs = ["thread_pool_test.cc"],
-    deps = [
-        "//tensorstore/util:executor",
-        "@com_google_absl//absl/synchronization",
-        "@com_google_absl//absl/time",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
 tensorstore_cc_library(
     name = "type_traits",
     hdrs = ["type_traits.h"],
@@ -1931,38 +1869,6 @@ tensorstore_cc_library(
     ],
 )
 
-tensorstore_cc_library(
-    name = "schedule_at",
-    srcs = ["schedule_at.cc"],
-    hdrs = ["schedule_at.h"],
-    deps = [
-        ":intrusive_red_black_tree",
-        ":no_destructor",
-        ":tagged_ptr",
-        ":thread",
-        "//tensorstore/internal/metrics",
-        "//tensorstore/internal/tracing",
-        "//tensorstore/util:stop_token",
-        "@com_google_absl//absl/base:core_headers",
-        "@com_google_absl//absl/functional:any_invocable",
-        "@com_google_absl//absl/synchronization",
-        "@com_google_absl//absl/time",
-    ],
-)
-
-tensorstore_cc_test(
-    name = "schedule_at_test",
-    size = "small",
-    srcs = ["schedule_at_test.cc"],
-    deps = [
-        ":schedule_at",
-        "//tensorstore/util:executor",
-        "//tensorstore/util:stop_token",
-        "@com_google_absl//absl/synchronization",
-        "@com_google_googletest//:gtest_main",
-    ],
-)
-
 tensorstore_cc_library(
     name = "multi_barrier",
     srcs = ["multi_barrier.cc"],
@@ -1978,7 +1884,7 @@ tensorstore_cc_test(
     srcs = ["multi_barrier_test.cc"],
     deps = [
         ":multi_barrier",
-        ":thread",
+        "//tensorstore/internal/thread",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/tensorstore/internal/cache/BUILD b/tensorstore/internal/cache/BUILD
index 1c9c4fd5d..40abcf4e4 100644
--- a/tensorstore/internal/cache/BUILD
+++ b/tensorstore/internal/cache/BUILD
@@ -1,5 +1,5 @@
-load("//bazel:tensorstore.bzl", "tensorstore_cc_binary", "tensorstore_cc_library", "tensorstore_cc_test")
 load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
+load("//bazel:tensorstore.bzl", "tensorstore_cc_binary", "tensorstore_cc_library", "tensorstore_cc_test")
 
 package(default_visibility = ["//tensorstore:internal_packages"])
 
@@ -360,7 +360,7 @@ tensorstore_cc_binary(
         "//tensorstore/index_space:transformed_array",
         "//tensorstore/internal:element_copy_function",
         "//tensorstore/internal:intrusive_ptr",
-        "//tensorstore/internal:thread_pool",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/kvstore:generation",
         "//tensorstore/util:executor",
         "//tensorstore/util:future",
@@ -405,7 +405,7 @@ tensorstore_cc_test(
         "//tensorstore/internal:memory",
         "//tensorstore/internal:meta",
         "//tensorstore/internal:queue_testutil",
-        "//tensorstore/internal:thread_pool",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/kvstore:generation",
         "//tensorstore/kvstore:mock_kvstore",
         "//tensorstore/kvstore:test_util",
diff --git a/tensorstore/internal/cache/chunk_cache_benchmark_test.cc b/tensorstore/internal/cache/chunk_cache_benchmark_test.cc
index eb3f6567b..8f8e55dbd 100644
--- a/tensorstore/internal/cache/chunk_cache_benchmark_test.cc
+++ b/tensorstore/internal/cache/chunk_cache_benchmark_test.cc
@@ -43,7 +43,7 @@
 #include "tensorstore/internal/cache/chunk_cache.h"
 #include "tensorstore/internal/element_copy_function.h"
 #include "tensorstore/internal/intrusive_ptr.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/progress.h"
 #include "tensorstore/rank.h"
diff --git a/tensorstore/internal/cache/chunk_cache_test.cc b/tensorstore/internal/cache/chunk_cache_test.cc
index 818f239c4..35f98655f 100644
--- a/tensorstore/internal/cache/chunk_cache_test.cc
+++ b/tensorstore/internal/cache/chunk_cache_test.cc
@@ -55,7 +55,7 @@
 #include "tensorstore/internal/memory.h"
 #include "tensorstore/internal/meta.h"
 #include "tensorstore/internal/queue_testutil.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/memory/memory_key_value_store.h"
 #include "tensorstore/kvstore/mock_kvstore.h"
diff --git a/tensorstore/internal/concurrency_resource.cc b/tensorstore/internal/concurrency_resource.cc
index e6bc804a3..65a916554 100644
--- a/tensorstore/internal/concurrency_resource.cc
+++ b/tensorstore/internal/concurrency_resource.cc
@@ -26,7 +26,7 @@
 #include "tensorstore/internal/json_binding/bindable.h"
 #include "tensorstore/internal/json_binding/json_binding.h"
 #include "tensorstore/internal/json_binding/std_optional.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/internal/type_traits.h"
 #include "tensorstore/util/executor.h"
 #include "tensorstore/util/result.h"
diff --git a/tensorstore/internal/concurrent_testutil.h b/tensorstore/internal/concurrent_testutil.h
index e2003003f..a539a5029 100644
--- a/tensorstore/internal/concurrent_testutil.h
+++ b/tensorstore/internal/concurrent_testutil.h
@@ -22,7 +22,7 @@
 #include <thread>  // NOLINT
 
 #include "tensorstore/internal/multi_barrier.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 
 namespace tensorstore {
 namespace internal {
diff --git a/tensorstore/internal/http/BUILD b/tensorstore/internal/http/BUILD
index b0e8f434a..0475bda82 100644
--- a/tensorstore/internal/http/BUILD
+++ b/tensorstore/internal/http/BUILD
@@ -47,9 +47,9 @@ tensorstore_cc_library(
         "//tensorstore/internal:cord_util",
         "//tensorstore/internal:env",
         "//tensorstore/internal:no_destructor",
-        "//tensorstore/internal:thread",
         "//tensorstore/internal/log:verbose_flag",
         "//tensorstore/internal/metrics",
+        "//tensorstore/internal/thread",
         "//tensorstore/util:future",
         "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/log:absl_log",
@@ -149,7 +149,7 @@ tensorstore_cc_test(
     deps = [
         ":curl_transport",
         ":transport_test_utils",
-        "//tensorstore/internal:thread",
+        "//tensorstore/internal/thread",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/log:absl_log",
         "@com_google_absl//absl/strings",
@@ -165,7 +165,7 @@ tensorstore_cc_test(
         ":curl_transport",
         ":http",
         ":transport_test_utils",
-        "//tensorstore/internal:thread",
+        "//tensorstore/internal/thread",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/log:absl_log",
diff --git a/tensorstore/internal/http/curl_transport.cc b/tensorstore/internal/http/curl_transport.cc
index f36b6b165..e4ab55da3 100644
--- a/tensorstore/internal/http/curl_transport.cc
+++ b/tensorstore/internal/http/curl_transport.cc
@@ -50,7 +50,7 @@
 #include "tensorstore/internal/metrics/gauge.h"
 #include "tensorstore/internal/metrics/histogram.h"
 #include "tensorstore/internal/no_destructor.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/util/future.h"
 
 namespace tensorstore {
diff --git a/tensorstore/internal/http/curl_transport_http2_test.cc b/tensorstore/internal/http/curl_transport_http2_test.cc
index ae1aed31e..57da1ed7a 100644
--- a/tensorstore/internal/http/curl_transport_http2_test.cc
+++ b/tensorstore/internal/http/curl_transport_http2_test.cc
@@ -36,7 +36,7 @@
 #include "tensorstore/internal/http/curl_transport.h"
 #include "tensorstore/internal/http/http_request.h"
 #include "tensorstore/internal/http/transport_test_utils.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 
 using ::tensorstore::internal_http::HttpRequestBuilder;
 using ::tensorstore::transport_test_utils::AcceptNonBlocking;
diff --git a/tensorstore/internal/http/curl_transport_test.cc b/tensorstore/internal/http/curl_transport_test.cc
index 999e1323b..9bc41ad3c 100644
--- a/tensorstore/internal/http/curl_transport_test.cc
+++ b/tensorstore/internal/http/curl_transport_test.cc
@@ -29,7 +29,7 @@
 #include "absl/log/absl_log.h"
 #include "absl/strings/str_cat.h"
 #include "tensorstore/internal/http/transport_test_utils.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 
 using ::tensorstore::internal_http::HttpRequestBuilder;
 using ::tensorstore::transport_test_utils::AcceptNonBlocking;
diff --git a/tensorstore/internal/multi_barrier_test.cc b/tensorstore/internal/multi_barrier_test.cc
index a50100d5b..ec76b2c28 100644
--- a/tensorstore/internal/multi_barrier_test.cc
+++ b/tensorstore/internal/multi_barrier_test.cc
@@ -17,7 +17,7 @@
 #include <type_traits>
 
 #include <gtest/gtest.h>
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 
 namespace internal = tensorstore::internal;
 
diff --git a/tensorstore/internal/thread/BUILD b/tensorstore/internal/thread/BUILD
new file mode 100644
index 000000000..223de0e6a
--- /dev/null
+++ b/tensorstore/internal/thread/BUILD
@@ -0,0 +1,101 @@
+load("//bazel:tensorstore.bzl", "tensorstore_cc_library", "tensorstore_cc_test")
+
+package(default_visibility = ["//tensorstore:internal_packages"])
+
+licenses(["notice"])
+
+tensorstore_cc_library(
+    name = "schedule_at",
+    srcs = ["schedule_at.cc"],
+    hdrs = ["schedule_at.h"],
+    deps = [
+        ":thread",
+        "//tensorstore/internal:attributes",
+        "//tensorstore/internal:intrusive_red_black_tree",
+        "//tensorstore/internal:no_destructor",
+        "//tensorstore/internal:tagged_ptr",
+        "//tensorstore/internal/metrics",
+        "//tensorstore/internal/tracing",
+        "//tensorstore/util:stop_token",
+        "@com_google_absl//absl/base:core_headers",
+        "@com_google_absl//absl/functional:any_invocable",
+        "@com_google_absl//absl/synchronization",
+        "@com_google_absl//absl/time",
+    ],
+)
+
+tensorstore_cc_test(
+    name = "schedule_at_test",
+    size = "small",
+    srcs = ["schedule_at_test.cc"],
+    deps = [
+        ":schedule_at",
+        "//tensorstore/util:stop_token",
+        "@com_google_absl//absl/synchronization",
+        "@com_google_absl//absl/time",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+tensorstore_cc_library(
+    name = "thread",
+    srcs = ["thread.cc"],
+    hdrs = ["thread.h"],
+    deps = [
+        "@com_google_absl//absl/functional:any_invocable",
+        "@com_google_absl//absl/log:absl_check",
+    ],
+)
+
+tensorstore_cc_test(
+    name = "thread_test",
+    srcs = ["thread_test.cc"],
+    deps = [
+        ":thread",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+tensorstore_cc_library(
+    name = "thread_pool",
+    srcs = ["thread_pool.cc"],
+    hdrs = ["thread_pool.h"],
+    deps = [
+        ":thread",
+        "//tensorstore/internal:attributes",
+        "//tensorstore/internal:intrusive_ptr",
+        "//tensorstore/internal:mutex",
+        "//tensorstore/internal:no_destructor",
+        "//tensorstore/internal/metrics",
+        "//tensorstore/util:executor",
+        "@com_google_absl//absl/base:core_headers",
+        "@com_google_absl//absl/functional:any_invocable",
+        "@com_google_absl//absl/log:absl_check",
+        "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/synchronization",
+        "@com_google_absl//absl/time",
+    ],
+)
+
+tensorstore_cc_library(
+    name = "thread_pool_test_cc",
+    testonly = 1,
+    textual_hdrs = ["thread_pool_test.inc"],
+    deps = [
+        "//tensorstore/util:executor",
+        "@com_google_absl//absl/synchronization",
+        "@com_google_absl//absl/time",
+        "@com_google_googletest//:gtest",
+    ],
+)
+
+tensorstore_cc_test(
+    name = "thread_pool_test",
+    size = "small",
+    srcs = ["thread_pool_test.cc"],
+    deps = [
+        ":thread_pool",
+        ":thread_pool_test_cc",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
diff --git a/tensorstore/internal/schedule_at.cc b/tensorstore/internal/thread/schedule_at.cc
similarity index 95%
rename from tensorstore/internal/schedule_at.cc
rename to tensorstore/internal/thread/schedule_at.cc
index fa2cf84b8..b7bbac87d 100644
--- a/tensorstore/internal/schedule_at.cc
+++ b/tensorstore/internal/thread/schedule_at.cc
@@ -12,8 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 
+#include <stdint.h>
+
+#include <algorithm>
+#include <atomic>
+#include <iterator>
+#include <memory>
 #include <utility>
 
 #include "absl/base/optimization.h"
@@ -22,13 +28,14 @@
 #include "absl/synchronization/mutex.h"
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
+#include "tensorstore/internal/attributes.h"
 #include "tensorstore/internal/intrusive_red_black_tree.h"
 #include "tensorstore/internal/metrics/gauge.h"
 #include "tensorstore/internal/metrics/histogram.h"
 #include "tensorstore/internal/metrics/value.h"
 #include "tensorstore/internal/no_destructor.h"
 #include "tensorstore/internal/tagged_ptr.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/internal/tracing/tracing.h"
 #include "tensorstore/util/stop_token.h"
 
@@ -39,16 +46,16 @@ namespace {
 using ScheduleAtTask = absl::AnyInvocable<void() &&>;
 
 auto& schedule_at_queued_ops = internal_metrics::Gauge<int64_t>::New(
-    "/tensorstore/internal/schedule_at/queued_ops",
+    "/tensorstore/internal/thread/schedule_at/queued_ops",
     "Operations in flight on the schedule_at thread");
 
 auto& schedule_at_next_event = internal_metrics::Value<absl::Time>::New(
-    "/tensorstore/internal/schedule_at/next_event",
+    "/tensorstore/internal/thread/schedule_at/next_event",
     "Time of the next in-flight schedule_at operation");
 
 auto& schedule_at_insert_histogram_ms =
     internal_metrics::Histogram<internal_metrics::DefaultBucketer>::New(
-        "/tensorstore/internal/schedule_at/insert_histogram_ms",
+        "/tensorstore/internal/thread/schedule_at/insert_histogram_ms",
         "Histogram of schedule_at insert delays (ms)");
 
 class DeadlineTaskQueue;
diff --git a/tensorstore/internal/schedule_at.h b/tensorstore/internal/thread/schedule_at.h
similarity index 87%
rename from tensorstore/internal/schedule_at.h
rename to tensorstore/internal/thread/schedule_at.h
index 7b4622e47..a09ef156a 100644
--- a/tensorstore/internal/schedule_at.h
+++ b/tensorstore/internal/thread/schedule_at.h
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef TENSORSTORE_INTERNAL_SCHEDULE_AT_H_
-#define TENSORSTORE_INTERNAL_SCHEDULE_AT_H_
+#ifndef TENSORSTORE_INTERNAL_THREAD_SCHEDULE_AT_H_
+#define TENSORSTORE_INTERNAL_THREAD_SCHEDULE_AT_H_
 
 #include "absl/functional/any_invocable.h"
 #include "absl/time/time.h"
@@ -32,4 +32,4 @@ void ScheduleAt(absl::Time target_time, absl::AnyInvocable<void() &&> task,
 }  // namespace internal
 }  // namespace tensorstore
 
-#endif  // TENSORSTORE_INTERNAL_SCHEDULE_AT_H_
+#endif  // TENSORSTORE_INTERNAL_THREAD_SCHEDULE_AT_H_
diff --git a/tensorstore/internal/schedule_at_test.cc b/tensorstore/internal/thread/schedule_at_test.cc
similarity index 96%
rename from tensorstore/internal/schedule_at_test.cc
rename to tensorstore/internal/thread/schedule_at_test.cc
index fa0aba029..4e50d2853 100644
--- a/tensorstore/internal/schedule_at_test.cc
+++ b/tensorstore/internal/thread/schedule_at_test.cc
@@ -12,14 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 
+#include <memory>
 #include <thread>  // NOLINT
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include "absl/synchronization/notification.h"
-#include "tensorstore/util/executor.h"
+#include "absl/time/clock.h"
+#include "absl/time/time.h"
 #include "tensorstore/util/stop_token.h"
 
 namespace {
diff --git a/tensorstore/internal/thread.cc b/tensorstore/internal/thread/thread.cc
similarity index 100%
rename from tensorstore/internal/thread.cc
rename to tensorstore/internal/thread/thread.cc
diff --git a/tensorstore/internal/thread.h b/tensorstore/internal/thread/thread.h
similarity index 100%
rename from tensorstore/internal/thread.h
rename to tensorstore/internal/thread/thread.h
diff --git a/tensorstore/internal/thread_pool.cc b/tensorstore/internal/thread/thread_pool.cc
similarity index 99%
rename from tensorstore/internal/thread_pool.cc
rename to tensorstore/internal/thread/thread_pool.cc
index 79ee19b85..83d0bc6d9 100644
--- a/tensorstore/internal/thread_pool.cc
+++ b/tensorstore/internal/thread/thread_pool.cc
@@ -31,7 +31,7 @@
 #include "tensorstore/internal/metrics/gauge.h"
 #include "tensorstore/internal/mutex.h"
 #include "tensorstore/internal/no_destructor.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/util/executor.h"
 
 namespace tensorstore {
diff --git a/tensorstore/internal/thread_pool.h b/tensorstore/internal/thread/thread_pool.h
similarity index 88%
rename from tensorstore/internal/thread_pool.h
rename to tensorstore/internal/thread/thread_pool.h
index 83ca869f3..26bb585e5 100644
--- a/tensorstore/internal/thread_pool.h
+++ b/tensorstore/internal/thread/thread_pool.h
@@ -12,8 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef TENSORSTORE_INTERNAL_THREAD_POOL_H_
-#define TENSORSTORE_INTERNAL_THREAD_POOL_H_
+#ifndef TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_H_
+#define TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_H_
 
 #include <stddef.h>
 
@@ -37,4 +37,4 @@ Executor DetachedThreadPool(
 }  // namespace internal
 }  // namespace tensorstore
 
-#endif  //  TENSORSTORE_INTERNAL_THREAD_POOL_H_
+#endif  //  TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_H_
diff --git a/tensorstore/internal/thread/thread_pool_benchmark.inc b/tensorstore/internal/thread/thread_pool_benchmark.inc
new file mode 100644
index 000000000..cc0214260
--- /dev/null
+++ b/tensorstore/internal/thread/thread_pool_benchmark.inc
@@ -0,0 +1,80 @@
+// Copyright 2020 The TensorStore Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_BENCHMARK_INC_
+#define THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_BENCHMARK_INC_
+
+#include <stddef.h>
+
+#include <algorithm>
+#include <vector>
+
+#include "testing/base/public/benchmark.h"
+#include "absl/random/random.h"
+#include "absl/synchronization/blocking_counter.h"
+#include "tensorstore/util/executor.h"
+
+namespace {
+
+using ::tensorstore::Executor;
+using ::tensorstore::internal::DetachedThreadPool;
+
+// This is a benchmark which enqueues a lot of items into a thread pool.
+// it doesn't have a goal of implementing an efficient matrix multiply; the
+// multiply is incidental.
+static void BM_ThreadPool_MatrixMultiply(benchmark::State& state) {
+  const size_t sz = state.range(0);
+  std::vector<float> A(sz * sz);
+  std::vector<float> B(sz * sz);
+  std::vector<float> C(sz * sz);
+
+  absl::BitGen rng;
+  std::generate(A.begin(), A.end(),
+                [&] { return absl::Gaussian<float>(rng, 0, 1); });
+  std::generate(B.begin(), B.end(),
+                [&] { return absl::Gaussian<float>(rng, 0, 1); });
+
+  for (auto s : state) {
+    absl::BlockingCounter done(sz * sz);
+    auto executor = DetachedThreadPool(state.range(1));
+    for (size_t i = 0; i < sz; i++) {
+      executor([&, i] {
+        for (size_t j = 0; j < sz; ++j) {
+          executor([&, i, j] {
+            float sum = 0;
+            for (size_t l = 0; l < sz; ++l) {
+              sum += A[i + l * sz] * B[l + j * sz];
+            }
+            C[i + j * sz] = sum;
+            done.DecrementCount();
+          });
+        }
+      });
+    }
+    done.Wait();
+  }
+  state.SetItemsProcessed(state.iterations() * sz * sz);
+}
+
+BENCHMARK(BM_ThreadPool_MatrixMultiply)  //
+    ->Args({256, 12})
+    ->Args({1024, 12})
+    ->Args({1024, 24})
+    ->Args({2048, 24})
+    ->Args({2048, 36})
+    ->UseRealTime();
+
+}  // namespace
+
+#endif  // THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_BENCHMARK_INC_
diff --git a/tensorstore/internal/thread/thread_pool_test.cc b/tensorstore/internal/thread/thread_pool_test.cc
new file mode 100644
index 000000000..5b106b763
--- /dev/null
+++ b/tensorstore/internal/thread/thread_pool_test.cc
@@ -0,0 +1,17 @@
+// Copyright 2020 The TensorStore Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "tensorstore/internal/thread/thread_pool.h"  // IWYU pragma: keep
+
+#include "tensorstore/internal/thread/thread_pool_test.inc"  // IWYU pragma: keep
diff --git a/tensorstore/internal/thread_pool_test.cc b/tensorstore/internal/thread/thread_pool_test.inc
similarity index 90%
rename from tensorstore/internal/thread_pool_test.cc
rename to tensorstore/internal/thread/thread_pool_test.inc
index 9a91df7fe..106414de8 100644
--- a/tensorstore/internal/thread_pool_test.cc
+++ b/tensorstore/internal/thread/thread_pool_test.inc
@@ -12,23 +12,25 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#ifndef THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_TEST_INC_
+#define THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_TEST_INC_
+
+#include <stddef.h>
+
 #include <atomic>
-#include <cstddef>
+#include <functional>
+#include <limits>
 #include <memory>
 #include <vector>
 
 #include <gtest/gtest.h>
 #include "absl/synchronization/notification.h"
 #include "absl/time/clock.h"
+#include "absl/time/time.h"
 #include "tensorstore/util/executor.h"
 
-namespace tensorstore {
-namespace internal {
-Executor DetachedThreadPool(std::size_t num_threads);
-}  // namespace internal
-}  // namespace tensorstore
-
 namespace {
+
 using ::tensorstore::Executor;
 using ::tensorstore::internal::DetachedThreadPool;
 
@@ -63,7 +65,7 @@ TEST(DetachedThreadPoolTest, Concurrent) {
 TEST(DetachedThreadPoolTest, ThreadLimit) {
   constexpr static size_t kThreadLimit = 3;
   auto executor = DetachedThreadPool(kThreadLimit);
-  std::atomic<std::size_t> num_running_tasks{0};
+  std::atomic<size_t> num_running_tasks{0};
   std::vector<absl::Notification> notifications(5);
   for (size_t i = 0; i < notifications.size(); ++i) {
     executor([&num_running_tasks, &notifications, i] {
@@ -116,3 +118,5 @@ TEST(DetachedThreadPoolTest, EnqueueFromTaskDestructor) {
 }
 
 }  // namespace
+
+#endif  // THIRD_PARTY_TENSORSTORE_INTERNAL_THREAD_THREAD_POOL_TEST_INC_
diff --git a/tensorstore/internal/thread_test.cc b/tensorstore/internal/thread/thread_test.cc
similarity index 95%
rename from tensorstore/internal/thread_test.cc
rename to tensorstore/internal/thread/thread_test.cc
index 16820babf..84b058c1d 100644
--- a/tensorstore/internal/thread_test.cc
+++ b/tensorstore/internal/thread/thread_test.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 
 #include <gtest/gtest.h>
 
diff --git a/tensorstore/kvstore/file/BUILD b/tensorstore/kvstore/file/BUILD
index e94abba7e..906ec2d7c 100644
--- a/tensorstore/kvstore/file/BUILD
+++ b/tensorstore/kvstore/file/BUILD
@@ -64,8 +64,8 @@ tensorstore_cc_test(
         "//tensorstore:context",
         "//tensorstore/internal:file_io_concurrency_resource",
         "//tensorstore/internal:test_util",
-        "//tensorstore/internal:thread",
         "//tensorstore/internal/os:filesystem",
+        "//tensorstore/internal/thread",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:generation",
         "//tensorstore/kvstore:generation_testutil",
diff --git a/tensorstore/kvstore/file/file_key_value_store_test.cc b/tensorstore/kvstore/file/file_key_value_store_test.cc
index b09f420d1..db4177b64 100644
--- a/tensorstore/kvstore/file/file_key_value_store_test.cc
+++ b/tensorstore/kvstore/file/file_key_value_store_test.cc
@@ -30,7 +30,7 @@
 #include "tensorstore/context.h"
 #include "tensorstore/internal/os/filesystem.h"
 #include "tensorstore/internal/test_util.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/generation_testutil.h"
 #include "tensorstore/kvstore/key_range.h"
diff --git a/tensorstore/kvstore/gcs_grpc/BUILD b/tensorstore/kvstore/gcs_grpc/BUILD
index b8039d9d8..be17842b0 100644
--- a/tensorstore/kvstore/gcs_grpc/BUILD
+++ b/tensorstore/kvstore/gcs_grpc/BUILD
@@ -15,7 +15,6 @@ tensorstore_cc_library(
         "//tensorstore/internal:data_copy_concurrency_resource",
         "//tensorstore/internal:intrusive_ptr",
         "//tensorstore/internal:retry",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal:uri_utils",
         "//tensorstore/internal/cache_key",
         "//tensorstore/internal/grpc:utils",
@@ -24,6 +23,7 @@ tensorstore_cc_library(
         "//tensorstore/internal/json_binding:bindable",
         "//tensorstore/internal/log:verbose_flag",
         "//tensorstore/internal/metrics",
+        "//tensorstore/internal/thread:schedule_at",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
@@ -121,7 +121,7 @@ tensorstore_cc_test(
     deps = [
         ":gcs_grpc",
         "//tensorstore/internal:no_destructor",
-        "//tensorstore/internal:thread",
+        "//tensorstore/internal/thread",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:generation",
         "//tensorstore/kvstore:test_util",
diff --git a/tensorstore/kvstore/gcs_grpc/gcs_grpc.cc b/tensorstore/kvstore/gcs_grpc/gcs_grpc.cc
index 966eb1e73..5a2fb7367 100644
--- a/tensorstore/kvstore/gcs_grpc/gcs_grpc.cc
+++ b/tensorstore/kvstore/gcs_grpc/gcs_grpc.cc
@@ -54,7 +54,7 @@
 #include "tensorstore/internal/metrics/counter.h"
 #include "tensorstore/internal/metrics/histogram.h"
 #include "tensorstore/internal/retry.h"
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/internal/uri_utils.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/driver.h"
diff --git a/tensorstore/kvstore/gcs_grpc/gcs_grpc_testbench_test.cc b/tensorstore/kvstore/gcs_grpc/gcs_grpc_testbench_test.cc
index 712f98274..57a0d5a43 100644
--- a/tensorstore/kvstore/gcs_grpc/gcs_grpc_testbench_test.cc
+++ b/tensorstore/kvstore/gcs_grpc/gcs_grpc_testbench_test.cc
@@ -26,7 +26,7 @@
 #include "absl/strings/cord.h"
 #include "absl/strings/str_cat.h"
 #include "tensorstore/internal/no_destructor.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/kvstore/gcs/gcs_testbench.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/kvstore.h"
diff --git a/tensorstore/kvstore/gcs_http/BUILD b/tensorstore/kvstore/gcs_http/BUILD
index 071ca44ba..e2386de47 100644
--- a/tensorstore/kvstore/gcs_http/BUILD
+++ b/tensorstore/kvstore/gcs_http/BUILD
@@ -22,7 +22,6 @@ tensorstore_cc_library(
         "//tensorstore/internal:path",
         "//tensorstore/internal:retries_context_resource",
         "//tensorstore/internal:retry",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal:source_location",
         "//tensorstore/internal:uri_utils",
         "//tensorstore/internal/cache_key",
@@ -36,6 +35,7 @@ tensorstore_cc_library(
         "//tensorstore/internal/metrics",
         "//tensorstore/internal/oauth2",
         "//tensorstore/internal/oauth2:google_auth_provider",
+        "//tensorstore/internal/thread:schedule_at",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
@@ -79,12 +79,12 @@ tensorstore_cc_test(
         "//tensorstore:context",
         "//tensorstore:json_serialization_options_base",
         "//tensorstore/internal:json_gtest",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal:uri_utils",
         "//tensorstore/internal/http",
         "//tensorstore/internal/http:curl_transport",
         "//tensorstore/internal/oauth2:google_auth_provider",
         "//tensorstore/internal/oauth2:google_auth_test_utils",
+        "//tensorstore/internal/thread:schedule_at",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:generation",
         "//tensorstore/kvstore:key_range",
@@ -188,8 +188,8 @@ tensorstore_cc_library(
     deps = [
         ":rate_limiter",
         "//tensorstore:data_type",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal/poly",
+        "//tensorstore/internal/thread:schedule_at",
         "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/log:absl_check",
         "@com_google_absl//absl/synchronization",
@@ -228,8 +228,8 @@ tensorstore_cc_test(
         ":gcs_http",
         "//tensorstore/internal:env",
         "//tensorstore/internal:no_destructor",
-        "//tensorstore/internal:thread",
         "//tensorstore/internal/http:transport_test_utils",
+        "//tensorstore/internal/thread",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:generation",
         "//tensorstore/kvstore:test_util",
diff --git a/tensorstore/kvstore/gcs_http/gcs_key_value_store.cc b/tensorstore/kvstore/gcs_http/gcs_key_value_store.cc
index f731d426e..f37875b55 100644
--- a/tensorstore/kvstore/gcs_http/gcs_key_value_store.cc
+++ b/tensorstore/kvstore/gcs_http/gcs_key_value_store.cc
@@ -56,8 +56,8 @@
 #include "tensorstore/internal/path.h"
 #include "tensorstore/internal/retries_context_resource.h"
 #include "tensorstore/internal/retry.h"
-#include "tensorstore/internal/schedule_at.h"
 #include "tensorstore/internal/source_location.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/internal/uri_utils.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/driver.h"
diff --git a/tensorstore/kvstore/gcs_http/gcs_key_value_store_test.cc b/tensorstore/kvstore/gcs_http/gcs_key_value_store_test.cc
index a462a558e..55ef0bfb7 100644
--- a/tensorstore/kvstore/gcs_http/gcs_key_value_store_test.cc
+++ b/tensorstore/kvstore/gcs_http/gcs_key_value_store_test.cc
@@ -43,7 +43,7 @@
 #include "tensorstore/internal/json_gtest.h"
 #include "tensorstore/internal/oauth2/google_auth_provider.h"
 #include "tensorstore/internal/oauth2/google_auth_test_utils.h"
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/internal/uri_utils.h"
 #include "tensorstore/json_serialization_options_base.h"
 #include "tensorstore/kvstore/gcs_http/gcs_mock.h"
diff --git a/tensorstore/kvstore/gcs_http/gcs_testbench_test.cc b/tensorstore/kvstore/gcs_http/gcs_testbench_test.cc
index c41a82864..246d15b7c 100644
--- a/tensorstore/kvstore/gcs_http/gcs_testbench_test.cc
+++ b/tensorstore/kvstore/gcs_http/gcs_testbench_test.cc
@@ -28,7 +28,7 @@
 #include "absl/strings/str_cat.h"
 #include "tensorstore/internal/env.h"
 #include "tensorstore/internal/no_destructor.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/kvstore.h"
 #include "tensorstore/kvstore/operations.h"
diff --git a/tensorstore/kvstore/gcs_http/scaling_rate_limiter.cc b/tensorstore/kvstore/gcs_http/scaling_rate_limiter.cc
index c7b0281a8..2911df270 100644
--- a/tensorstore/kvstore/gcs_http/scaling_rate_limiter.cc
+++ b/tensorstore/kvstore/gcs_http/scaling_rate_limiter.cc
@@ -21,7 +21,7 @@
 #include "absl/synchronization/mutex.h"
 #include "absl/time/time.h"
 #include "tensorstore/data_type.h"
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/kvstore/gcs_http/rate_limiter.h"
 
 namespace tensorstore {
diff --git a/tensorstore/kvstore/neuroglancer_uint64_sharded/BUILD b/tensorstore/kvstore/neuroglancer_uint64_sharded/BUILD
index 882c307f7..acea651ac 100644
--- a/tensorstore/kvstore/neuroglancer_uint64_sharded/BUILD
+++ b/tensorstore/kvstore/neuroglancer_uint64_sharded/BUILD
@@ -187,10 +187,10 @@ tensorstore_cc_test(
         "//tensorstore/internal:global_initializer",
         "//tensorstore/internal:intrusive_ptr",
         "//tensorstore/internal:test_util",
-        "//tensorstore/internal:thread_pool",
         "//tensorstore/internal/cache",
         "//tensorstore/internal/cache:kvs_backed_cache_testutil",
         "//tensorstore/internal/compression:zlib",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
diff --git a/tensorstore/kvstore/neuroglancer_uint64_sharded/neuroglancer_uint64_sharded_test.cc b/tensorstore/kvstore/neuroglancer_uint64_sharded/neuroglancer_uint64_sharded_test.cc
index 084692192..49433115b 100644
--- a/tensorstore/kvstore/neuroglancer_uint64_sharded/neuroglancer_uint64_sharded_test.cc
+++ b/tensorstore/kvstore/neuroglancer_uint64_sharded/neuroglancer_uint64_sharded_test.cc
@@ -41,7 +41,7 @@
 #include "tensorstore/internal/global_initializer.h"
 #include "tensorstore/internal/intrusive_ptr.h"
 #include "tensorstore/internal/test_util.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/generation_testutil.h"
diff --git a/tensorstore/kvstore/ocdbt/io/BUILD b/tensorstore/kvstore/ocdbt/io/BUILD
index 8380454c1..ad04ccfae 100644
--- a/tensorstore/kvstore/ocdbt/io/BUILD
+++ b/tensorstore/kvstore/ocdbt/io/BUILD
@@ -15,8 +15,8 @@ cc_library(
         "//tensorstore:transaction",
         "//tensorstore/internal:flat_cord_builder",
         "//tensorstore/internal:intrusive_ptr",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal/log:verbose_flag",
+        "//tensorstore/internal/thread:schedule_at",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
@@ -44,7 +44,7 @@ tensorstore_cc_test(
     srcs = ["coalesce_kvstore_test.cc"],
     deps = [
         ":coalesce_kvstore",
-        "//tensorstore/internal:thread_pool",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:mock_kvstore",
         "//tensorstore/kvstore:test_util",
diff --git a/tensorstore/kvstore/ocdbt/io/coalesce_kvstore.cc b/tensorstore/kvstore/ocdbt/io/coalesce_kvstore.cc
index 8db1b4469..82b550172 100644
--- a/tensorstore/kvstore/ocdbt/io/coalesce_kvstore.cc
+++ b/tensorstore/kvstore/ocdbt/io/coalesce_kvstore.cc
@@ -40,7 +40,7 @@
 #include "tensorstore/internal/flat_cord_builder.h"
 #include "tensorstore/internal/intrusive_ptr.h"
 #include "tensorstore/internal/log/verbose_flag.h"
-#include "tensorstore/internal/schedule_at.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/driver.h"
 #include "tensorstore/kvstore/generation.h"
diff --git a/tensorstore/kvstore/ocdbt/io/coalesce_kvstore_test.cc b/tensorstore/kvstore/ocdbt/io/coalesce_kvstore_test.cc
index df3b47472..774daef24 100644
--- a/tensorstore/kvstore/ocdbt/io/coalesce_kvstore_test.cc
+++ b/tensorstore/kvstore/ocdbt/io/coalesce_kvstore_test.cc
@@ -18,7 +18,7 @@
 #include <gtest/gtest.h>
 #include "absl/strings/cord.h"
 #include "absl/time/time.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/kvstore/kvstore.h"
 #include "tensorstore/kvstore/mock_kvstore.h"
 #include "tensorstore/kvstore/operations.h"
diff --git a/tensorstore/kvstore/s3/BUILD b/tensorstore/kvstore/s3/BUILD
index f0cedd24c..9cc312ddb 100644
--- a/tensorstore/kvstore/s3/BUILD
+++ b/tensorstore/kvstore/s3/BUILD
@@ -30,7 +30,6 @@ tensorstore_cc_library(
         "//tensorstore/internal:data_copy_concurrency_resource",
         "//tensorstore/internal:intrusive_ptr",
         "//tensorstore/internal:retry",
-        "//tensorstore/internal:schedule_at",
         "//tensorstore/internal:source_location",
         "//tensorstore/internal:uri_utils",
         "//tensorstore/internal/cache_key",
@@ -40,6 +39,7 @@ tensorstore_cc_library(
         "//tensorstore/internal/json_binding",
         "//tensorstore/internal/log:verbose_flag",
         "//tensorstore/internal/metrics",
+        "//tensorstore/internal/thread:schedule_at",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
diff --git a/tensorstore/kvstore/s3/s3_key_value_store.cc b/tensorstore/kvstore/s3/s3_key_value_store.cc
index 5a9026a47..3d74da894 100644
--- a/tensorstore/kvstore/s3/s3_key_value_store.cc
+++ b/tensorstore/kvstore/s3/s3_key_value_store.cc
@@ -49,8 +49,8 @@
 #include "tensorstore/internal/metrics/counter.h"
 #include "tensorstore/internal/metrics/histogram.h"
 #include "tensorstore/internal/retry.h"
-#include "tensorstore/internal/schedule_at.h"
 #include "tensorstore/internal/source_location.h"
+#include "tensorstore/internal/thread/schedule_at.h"
 #include "tensorstore/internal/uri_utils.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/gcs/validate.h"
diff --git a/tensorstore/kvstore/zarr3_sharding_indexed/BUILD b/tensorstore/kvstore/zarr3_sharding_indexed/BUILD
index 7d66d4c0b..2665c7e14 100644
--- a/tensorstore/kvstore/zarr3_sharding_indexed/BUILD
+++ b/tensorstore/kvstore/zarr3_sharding_indexed/BUILD
@@ -87,10 +87,10 @@ tensorstore_cc_test(
         "//tensorstore/internal:global_initializer",
         "//tensorstore/internal:intrusive_ptr",
         "//tensorstore/internal:test_util",
-        "//tensorstore/internal:thread_pool",
         "//tensorstore/internal/cache",
         "//tensorstore/internal/cache:kvs_backed_cache_testutil",
         "//tensorstore/internal/riegeli:digest_suffixed_writer",
+        "//tensorstore/internal/thread:thread_pool",
         "//tensorstore/kvstore",
         "//tensorstore/kvstore:byte_range",
         "//tensorstore/kvstore:generation",
diff --git a/tensorstore/kvstore/zarr3_sharding_indexed/zarr3_sharding_indexed_test.cc b/tensorstore/kvstore/zarr3_sharding_indexed/zarr3_sharding_indexed_test.cc
index 9cc49bfb6..8e71b0aa9 100644
--- a/tensorstore/kvstore/zarr3_sharding_indexed/zarr3_sharding_indexed_test.cc
+++ b/tensorstore/kvstore/zarr3_sharding_indexed/zarr3_sharding_indexed_test.cc
@@ -48,7 +48,7 @@
 #include "tensorstore/internal/intrusive_ptr.h"
 #include "tensorstore/internal/riegeli/digest_suffixed_writer.h"
 #include "tensorstore/internal/test_util.h"
-#include "tensorstore/internal/thread_pool.h"
+#include "tensorstore/internal/thread/thread_pool.h"
 #include "tensorstore/kvstore/byte_range.h"
 #include "tensorstore/kvstore/generation.h"
 #include "tensorstore/kvstore/generation_testutil.h"
diff --git a/tensorstore/util/execution/BUILD b/tensorstore/util/execution/BUILD
index 01f23f2c9..3eeda8ad5 100644
--- a/tensorstore/util/execution/BUILD
+++ b/tensorstore/util/execution/BUILD
@@ -136,8 +136,7 @@ tensorstore_cc_test(
         ":execution",
         ":sender_testutil",
         ":sync_flow_sender",
-        "//tensorstore/internal:mutex",
-        "//tensorstore/internal:thread",
+        "//tensorstore/internal/thread",
         "@com_google_googletest//:gtest_main",
     ],
 )
diff --git a/tensorstore/util/execution/sync_flow_sender_test.cc b/tensorstore/util/execution/sync_flow_sender_test.cc
index 6d9a5a656..3dbbd0d7b 100644
--- a/tensorstore/util/execution/sync_flow_sender_test.cc
+++ b/tensorstore/util/execution/sync_flow_sender_test.cc
@@ -14,26 +14,27 @@
 
 #include "tensorstore/util/execution/sync_flow_sender.h"
 
+#include <stddef.h>
+
 #include <string>
 #include <vector>
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
-#include "tensorstore/internal/mutex.h"
-#include "tensorstore/internal/thread.h"
+#include "tensorstore/internal/thread/thread.h"
 #include "tensorstore/util/execution/execution.h"
 #include "tensorstore/util/execution/sender_testutil.h"
 
 namespace {
 
 struct ConcurrentSender {
-  std::size_t num_threads;
+  size_t num_threads;
   bool error;
   template <typename Receiver>
   void submit(Receiver receiver) {
     tensorstore::execution::set_starting(receiver, [] {});
     std::vector<tensorstore::internal::Thread> threads;
-    for (std::size_t i = 0; i < num_threads; ++i) {
+    for (size_t i = 0; i < num_threads; ++i) {
       threads.emplace_back(tensorstore::internal::Thread(
           {"sender"},
           [i, &receiver] { tensorstore::execution::set_value(receiver, i); }));
@@ -50,7 +51,7 @@ struct ConcurrentSender {
 
 TEST(SyncFlowSender, Values) {
   std::vector<std::string> log;
-  const std::size_t num_threads = 10;
+  const size_t num_threads = 10;
   tensorstore::execution::submit(
       tensorstore::MakeSyncFlowSender(
           ConcurrentSender{num_threads, /*.error=*/false}),
@@ -69,7 +70,7 @@ TEST(SyncFlowSender, Values) {
 
 TEST(SyncFlowSender, Error) {
   std::vector<std::string> log;
-  const std::size_t num_threads = 10;
+  const size_t num_threads = 10;
   tensorstore::execution::submit(
       tensorstore::MakeSyncFlowSender(
           ConcurrentSender{num_threads, /*.error=*/true}),