diff --git a/backend/app/services/ext_fanout.py b/backend/app/services/ext_fanout.py
index 7d86290b..baeda0bc 100644
--- a/backend/app/services/ext_fanout.py
+++ b/backend/app/services/ext_fanout.py
@@ -75,6 +75,13 @@ def _raise_on_envelope_error(data: Any) -> None:
 
 
 async def fetch_fanout_rows(config: ExtConfig, target_date=None) -> list[dict]:
+    from app.services.ext_pull import _pull_client_scope
+
+    async with _pull_client_scope():
+        return await _fetch_fanout_rows(config, target_date)
+
+
+async def _fetch_fanout_rows(config: ExtConfig, target_date=None) -> list[dict]:
     """执行两级拉取并反转为「成员 → 类别清单」行。"""
     from app.services.ext_pull import (
         _append_query_params,
diff --git a/backend/app/services/ext_pull.py b/backend/app/services/ext_pull.py
index a3f78373..c55f523b 100644
--- a/backend/app/services/ext_pull.py
+++ b/backend/app/services/ext_pull.py
@@ -5,6 +5,8 @@ import asyncio
 import json
 import logging
 import threading
+from contextlib import asynccontextmanager
+from contextvars import ContextVar
 from datetime import UTC, date, datetime, timezone
 from functools import reduce
 from pathlib import Path
@@ -22,6 +24,22 @@ from app.services.ext_data import (
 
 logger = logging.getLogger(__name__)
 
+_pull_client: ContextVar[httpx.AsyncClient | None] = ContextVar("ext_pull_client", default=None)
+
+
+@asynccontextmanager
+async def _pull_client_scope():
+    client = _pull_client.get()
+    if client is not None:
+        yield client
+        return
+    async with httpx.AsyncClient() as client:
+        token = _pull_client.set(client)
+        try:
+            yield client
+        finally:
+            _pull_client.reset(token)
+
 
 def outbound_headers(user_headers: dict[str, str] | None = None) -> dict[str, str]:
     """扩展数据出站请求的默认标识头。
@@ -230,10 +248,10 @@ async def _request_json(
     # getattr 兜底测试用的简化 pull 对象
     timeout = getattr(pull, "timeout_seconds", None)
     timeout = timeout if isinstance(timeout, (int, float)) and timeout > 0 else 30
-    async with httpx.AsyncClient(timeout=timeout) as client:
+    async with _pull_client_scope() as client:
         headers = outbound_headers(pull.headers)
         url = _apply_auth(config_id, pull.auth, url, headers)
-        kwargs: dict[str, Any] = {"headers": headers}
+        kwargs: dict[str, Any] = {"headers": headers, "timeout": timeout}
 
         if pull.method.upper() == "POST" and pull.body:
             kwargs["content"] = pull.body
@@ -270,6 +288,11 @@ def _parse_rows_payload(config: ExtConfig, pull: PullConfig, data: Any) -> list[
 
 
 async def fetch_rows_for_date(config: ExtConfig, target_date: date) -> list[dict]:
+    async with _pull_client_scope():
+        return await _fetch_rows_for_date(config, target_date)
+
+
+async def _fetch_rows_for_date(config: ExtConfig, target_date: date) -> list[dict]:
     """按日期请求外部 API 并解析为行 (不写盘)。空数据返回 []。
 
     与 fetch_and_ingest 共用同一解析链 (response_path/字段映射/关联字段校验),
@@ -377,6 +400,16 @@ async def backfill_history(
     data_dir,
     start: date,
     end: date,
+) -> dict:
+    async with _pull_client_scope():
+        return await _backfill_history(config, data_dir, start, end)
+
+
+async def _backfill_history(
+    config: ExtConfig,
+    data_dir,
+    start: date,
+    end: date,
 ) -> dict:
     """按本地交易日逐日回补 timeseries 历史分区 (幂等, 已有分区跳过)。
 
diff --git a/backend/scripts/benchmark_ext_pull_client.py b/backend/scripts/benchmark_ext_pull_client.py
new file mode 100644
index 00000000..1924c3e7
--- /dev/null
+++ b/backend/scripts/benchmark_ext_pull_client.py
@@ -0,0 +1,74 @@
+"""Compare per-request HTTP clients with one client per pull using a mock server.
+
+Run: uv run --frozen python -m scripts.benchmark_ext_pull_client
+No external network requests or user data are used.
+"""
+from __future__ import annotations
+
+import asyncio
+import statistics
+import time
+from datetime import date
+
+import httpx
+
+from app.services import ext_pull
+from app.services.ext_data import ExtConfig, PullConfig
+
+PAGES = 30
+RUNS = 5
+
+
+async def run(shared: bool) -> tuple[float, int, int]:
+    clients = 0
+    requests = 0
+    real_client = httpx.AsyncClient
+
+    def respond(request: httpx.Request) -> httpx.Response:
+        nonlocal requests
+        requests += 1
+        page = int(request.url.params["page"])
+        return httpx.Response(200, json=[{"symbol": "000001.SZ"}] if page <= PAGES else [])
+
+    def factory(*args, **kwargs):
+        nonlocal clients
+        clients += 1
+        return real_client(*args, transport=httpx.MockTransport(respond), **kwargs)
+
+    original = ext_pull.httpx.AsyncClient
+    ext_pull.httpx.AsyncClient = factory
+    config = ExtConfig(
+        id="benchmark", label="benchmark", mode="timeseries", fields=[],
+        pull=PullConfig(url="https://example.test/rank", page_param="page", max_pages=PAGES + 1),
+    )
+    try:
+        started = time.perf_counter()
+        if shared:
+            rows = await ext_pull.fetch_rows_for_date(config, date(2026, 9, 1))
+        else:
+            for page in range(1, PAGES + 2):
+                payload = await ext_pull._request_json(config.pull, config.id, extra_params={"page": str(page)})
+                if not payload:
+                    break
+                if page == 1:
+                    rows = []
+                rows.extend(payload)
+        elapsed = time.perf_counter() - started
+        assert len(rows) == PAGES and requests == PAGES + 1
+        return elapsed, clients, requests
+    finally:
+        ext_pull.httpx.AsyncClient = original
+
+
+async def main() -> None:
+    timings: dict[bool, list[float]] = {False: [], True: []}
+    for _ in range(RUNS):
+        for shared in (False, True):
+            elapsed, clients, requests = await run(shared)
+            timings[shared].append(elapsed)
+            print(f"{'shared' if shared else 'per-request'}: {elapsed:.4f}s, {requests} requests, {clients} clients")
+    print(f"median: per-request={statistics.median(timings[False]):.4f}s, shared={statistics.median(timings[True]):.4f}s")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())
diff --git a/backend/tests/test_ext_pull_pagination.py b/backend/tests/test_ext_pull_pagination.py
index 375549f0..091707c6 100644
--- a/backend/tests/test_ext_pull_pagination.py
+++ b/backend/tests/test_ext_pull_pagination.py
@@ -3,8 +3,10 @@ max_pages 安全上限、非分页配置行为不变。mock _request_json, 不
 """
 from __future__ import annotations
 
+import asyncio
 from datetime import date
 
+import httpx
 import pytest
 
 from app.services import ext_pull
@@ -38,6 +40,107 @@ def _install_pages(monkeypatch: pytest.MonkeyPatch, pages: dict[int, list[dict]]
 TARGET = date(2026, 9, 20)
 
 
+async def test_pagination_reuses_client_and_closes_on_failure(monkeypatch: pytest.MonkeyPatch) -> None:
+    created = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        page = request.url.params["page"]
+        if page == "2":
+            return httpx.Response(503)
+        return httpx.Response(200, json={"data": [{"symbol": "000001.SZ"}]})
+
+    real_client = httpx.AsyncClient
+
+    def client_factory(*args, **kwargs):
+        client = real_client(*args, transport=httpx.MockTransport(handler), **kwargs)
+        created.append(client)
+        return client
+
+    monkeypatch.setattr(ext_pull.httpx, "AsyncClient", client_factory)
+    cfg = _cfg(PullConfig(url="https://example.test/rank", response_path="data", page_param="page"))
+    with pytest.raises(httpx.HTTPStatusError):
+        await ext_pull.fetch_rows_for_date(cfg, TARGET)
+    assert len(created) == 1
+    assert created[0].is_closed
+
+
+async def test_fanout_reuses_client_for_concurrent_requests(monkeypatch: pytest.MonkeyPatch) -> None:
+    from app.services.ext_fanout import fetch_fanout_rows
+
+    created = []
+    real_client = httpx.AsyncClient
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.url.path == "/catalog":
+            return httpx.Response(200, json=[{"id": "one"}, {"id": "two"}])
+        return httpx.Response(200, json={"items": [{"symbol": request.url.params["id"]}]})
+
+    def client_factory(*args, **kwargs):
+        client = real_client(*args, transport=httpx.MockTransport(handler), **kwargs)
+        created.append(client)
+        return client
+
+    monkeypatch.setattr(ext_pull.httpx, "AsyncClient", client_factory)
+    fanout = {
+        "url": "https://example.test/members", "param": "id", "id_field": "id",
+        "items_path": "items", "member_id_field": "symbol", "symbol_col": "symbol",
+        "name_col": "name", "value_col": "groups",
+    }
+    cfg = _cfg(PullConfig(url="https://example.test/catalog", fanout=fanout))
+    rows = await fetch_fanout_rows(cfg)
+    assert {row["symbol"] for row in rows} == {"one", "two"}
+    assert len(created) == 1
+    assert created[0].is_closed
+
+
+async def test_cancelled_pull_closes_client(monkeypatch: pytest.MonkeyPatch) -> None:
+    created = []
+    real_client = httpx.AsyncClient
+
+    async def handler(request: httpx.Request) -> httpx.Response:
+        raise asyncio.CancelledError
+
+    def client_factory(*args, **kwargs):
+        client = real_client(*args, transport=httpx.MockTransport(handler), **kwargs)
+        created.append(client)
+        return client
+
+    monkeypatch.setattr(ext_pull.httpx, "AsyncClient", client_factory)
+    with pytest.raises(asyncio.CancelledError):
+        await ext_pull.fetch_rows_for_date(_cfg(PullConfig(url="https://example.test/rank")), TARGET)
+    assert len(created) == 1
+    assert created[0].is_closed
+
+
+async def test_backfill_reuses_client_across_days(monkeypatch: pytest.MonkeyPatch, tmp_path) -> None:
+    created = []
+    real_client = httpx.AsyncClient
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        return httpx.Response(200, json=[{"symbol": "000001.SZ", "date": request.url.params["date"]}])
+
+    def client_factory(*args, **kwargs):
+        client = real_client(*args, transport=httpx.MockTransport(handler), **kwargs)
+        created.append(client)
+        return client
+
+    monkeypatch.setattr(ext_pull.httpx, "AsyncClient", client_factory)
+    monkeypatch.setattr(
+        "app.services.dragon_tiger._local_trading_days",
+        lambda _: [date(2026, 9, 17), date(2026, 9, 18)],
+    )
+
+    async def no_sleep(_):
+        return None
+
+    monkeypatch.setattr(ext_pull.asyncio, "sleep", no_sleep)
+    cfg = _cfg(PullConfig(url="https://example.test/rank", date_param="date"))
+    result = await ext_pull.backfill_history(cfg, tmp_path, date(2026, 9, 17), date(2026, 9, 18))
+    assert result["fetched"] == 2
+    assert len(created) == 1
+    assert created[0].is_closed
+
+
 async def test_pagination_collects_pages_and_stops_on_short_page(monkeypatch: pytest.MonkeyPatch) -> None:
     # page_size=2: 第 2 页只有 1 行 (短页) → 停, 不再请求第 3 页
     pull = PullConfig(
diff --git a/backend/tests/test_ext_pull_timeout_config.py b/backend/tests/test_ext_pull_timeout_config.py
index cc64423b..3cf39606 100644
--- a/backend/tests/test_ext_pull_timeout_config.py
+++ b/backend/tests/test_ext_pull_timeout_config.py
@@ -10,9 +10,8 @@ from types import SimpleNamespace
 
 import pytest
 
-from app.services.ext_data import PullConfig
 from app.services import ext_pull
-
+from app.services.ext_data import PullConfig
 
 # ── 模型: 默认值 / 序列化 / 非法值归一 ──────────────────────────────
 
@@ -47,9 +46,10 @@ class _FakeResponse:
 
 
 class _FakeClient:
-    """捕获 timeout 构造参数的 httpx.AsyncClient 替身。"""
+    """捕获每次请求的 timeout。"""
 
     last_timeout: object = None
+    request_timeout: object = None
 
     def __init__(self, timeout=None, **kwargs):
         _FakeClient.last_timeout = timeout
@@ -61,6 +61,7 @@ class _FakeClient:
         return False
 
     async def request(self, method, url, **kwargs):
+        _FakeClient.request_timeout = kwargs.get("timeout")
         return _FakeResponse()
 
 
@@ -69,7 +70,7 @@ async def test_request_json_uses_configured_timeout(monkeypatch):
 
     pull = PullConfig(url="https://x", timeout_seconds=90)
     await ext_pull._request_json(pull, "cfg1")
-    assert _FakeClient.last_timeout == 90
+    assert _FakeClient.request_timeout == 90
 
 
 async def test_request_json_defaults_to_30_without_attr(monkeypatch):
@@ -81,7 +82,7 @@ async def test_request_json_defaults_to_30_without_attr(monkeypatch):
         method="GET", body=None, auth=None,
     )
     await ext_pull._request_json(pull, "cfg1")
-    assert _FakeClient.last_timeout == 30
+    assert _FakeClient.request_timeout == 30
 
 
 # ── 探测路径: detect-url 请求体带 timeout_seconds ───────────────────
diff --git a/docs/backend-data-performance-plan.md b/docs/backend-data-performance-plan.md
new file mode 100644
index 00000000..6f28db3c
--- /dev/null
+++ b/docs/backend-data-performance-plan.md
@@ -0,0 +1,33 @@
+# 后端数据获取与处理性能计划
+
+本计划只处理已排查到的四条链路。按相同环境、相同数据量对比修改前后耗时和内存；没有实测数据前不宣称整套回测或页面加速。每项单独验证、单独提交，保留数据口径、缓存失效和原子写语义。
+
+## 1. 扩展数据拉取复用连接（本次实施）
+
+- 场景：扩展表分页、历史回补和两级拉取会连续请求同一数据源。
+- 问题：每次请求都新建 HTTP 客户端，重复建立连接。
+- 改动：一次拉取任务内共用客户端，请求仍按各配置单独设置超时；任务结束、失败或取消时关闭。保留现有限流、重试、鉴权和两级拉取并发上限。
+- 验证：模拟接口分别覆盖分页、按天回补、并发明细与失败关闭；对比请求数、客户端创建次数和耗时。真实网络收益需另行测量。
+
+## 2. 扩展表按范围读取时减少无用数据（待测）
+
+- 场景：按日期范围查询扩展数据明细或字段取值。
+- 问题：先读取所有分区和列并合并，然后才过滤、选列、分页。
+- 计划：先测分区数、读取耗时、峰值内存；若读取占主要时间，再将必要的过滤与选列提前，并只把返回页转为 Python 对象。
+- 验证：跨分区字段缺失、日期列补全、排序、总数与分页结果须与现有实现一致。
+
+## 3. 日 K 流式同步减少临时文件读写（待测）
+
+- 场景：按批获取历史日 K，分日暂存后再写正式分区。
+- 问题：临时文件写入后按日读回，再与正式分区合并写入。
+- 计划：先分别记录下载、暂存、读回和合并耗时与文件数；只有落盘占比明显时才优化批量提交。
+- 验证：部分批次失败不能破坏旧数据；原子写和并发更新语义不变。
+
+## 4. 扩展表更新与历史计算减少全量重复工作（待测）
+
+- 场景：扩展表频繁更新快照/当日分区，策略读取多日扩展因子。
+- 问题：每次写入都读取并合并已有文件；缓存失效后历史因子逐分区加载完整表。
+- 计划：先按更新频率、分区大小测写放大和读取峰值；再评估只读必要日期/字段或减少重复合并。
+- 验证：同日去重、历史时点对齐、缓存失效和失败恢复不变。
+
+现有 `market-data-performance-checklist.md` 是另一份未提交的工作文件，本计划不修改它。
\ No newline at end of file