diff --git a/backend/app/api/public/docs_page.py b/backend/app/api/public/docs_page.py
index 7018c46..5009620 100644
--- a/backend/app/api/public/docs_page.py
+++ b/backend/app/api/public/docs_page.py
@@ -52,17 +52,18 @@ def _build_docs_html(*, base_url: str) -> str:
   <title>Random Mage Docs</title>
   <style>
     :root {{
-      --bg: #0b1220;
-      --card: rgba(255, 255, 255, 0.06);
-      --card-2: rgba(255, 255, 255, 0.08);
-      --border: rgba(255, 255, 255, 0.12);
-      --text: rgba(255, 255, 255, 0.92);
-      --muted: rgba(255, 255, 255, 0.72);
-      --muted2: rgba(255, 255, 255, 0.60);
-      --link: #7dd3fc;
-      --accent: #a78bfa;
-      --ok: #34d399;
-      --warn: #fbbf24;
+      /* Clay / paper-like palette */
+      --bg: #f4efe6;
+      --card: rgba(255, 250, 243, 0.78);
+      --card-2: rgba(255, 250, 243, 0.92);
+      --border: rgba(58, 38, 26, 0.14);
+      --text: rgba(43, 29, 22, 0.94);
+      --muted: rgba(67, 51, 44, 0.78);
+      --muted2: rgba(67, 51, 44, 0.66);
+      --link: #a2522c;
+      --accent: #c07046;
+      --ok: #1f7a56;
+      --warn: #b45309;
       --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
       --sans: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji",
         "Segoe UI Emoji";
@@ -74,9 +75,9 @@ def _build_docs_html(*, base_url: str) -> str:
       font-family: var(--sans);
       color: var(--text);
       background:
-        radial-gradient(1000px 600px at 15% 10%, rgba(167, 139, 250, 0.22), transparent 55%),
-        radial-gradient(900px 520px at 85% 0%, rgba(125, 211, 252, 0.18), transparent 60%),
-        radial-gradient(700px 700px at 60% 85%, rgba(52, 211, 153, 0.12), transparent 55%),
+        radial-gradient(1000px 620px at 12% 8%, rgba(192, 112, 70, 0.18), transparent 58%),
+        radial-gradient(900px 560px at 88% 0%, rgba(162, 82, 44, 0.14), transparent 60%),
+        radial-gradient(760px 760px at 60% 92%, rgba(31, 122, 86, 0.10), transparent 58%),
         var(--bg);
     }}
 
@@ -88,13 +89,16 @@ def _build_docs_html(*, base_url: str) -> str:
       margin: 0 auto;
       padding: 32px 20px 64px;
     }}
+    @media (max-width: 520px) {{
+      .wrap {{ padding: 22px 14px 46px; }}
+    }}
 
     .hero {{
       padding: 18px 18px 16px;
       border: 1px solid var(--border);
-      background: linear-gradient(180deg, rgba(255,255,255,0.08), rgba(255,255,255,0.04));
+      background: linear-gradient(180deg, rgba(255,250,243,0.92), rgba(255,250,243,0.70));
       border-radius: 14px;
-      backdrop-filter: blur(10px);
+      box-shadow: 0 10px 30px rgba(40, 24, 16, 0.10);
     }}
 
     .hero h1 {{
@@ -102,6 +106,9 @@ def _build_docs_html(*, base_url: str) -> str:
       font-size: 22px;
       letter-spacing: 0.2px;
     }}
+    @media (max-width: 520px) {{
+      .hero h1 {{ font-size: 20px; }}
+    }}
     .hero p {{
       margin: 10px 0 0;
       color: var(--muted);
@@ -123,6 +130,10 @@ def _build_docs_html(*, base_url: str) -> str:
       background: var(--card);
       border-radius: 14px;
       padding: 16px 16px 14px;
+      box-shadow: 0 10px 30px rgba(40, 24, 16, 0.06);
+    }}
+    @media (max-width: 520px) {{
+      .card {{ padding: 14px 14px 12px; }}
     }}
     .card h2 {{
       font-size: 16px;
@@ -142,8 +153,8 @@ def _build_docs_html(*, base_url: str) -> str:
       padding: 2px 6px;
       border-radius: 8px;
       border: 1px solid var(--border);
-      background: rgba(0, 0, 0, 0.18);
-      color: rgba(255,255,255,0.86);
+      background: rgba(43, 29, 22, 0.06);
+      color: rgba(43, 29, 22, 0.92);
     }}
 
     pre {{
@@ -151,12 +162,15 @@ def _build_docs_html(*, base_url: str) -> str:
       padding: 12px 12px;
       border-radius: 12px;
       border: 1px solid var(--border);
-      background: rgba(0, 0, 0, 0.22);
+      background: rgba(43, 29, 22, 0.06);
       overflow: auto;
       font-family: var(--mono);
       font-size: 12px;
       line-height: 1.55;
-      color: rgba(255,255,255,0.88);
+      color: rgba(43, 29, 22, 0.92);
+    }}
+    @media (max-width: 520px) {{
+      pre {{ font-size: 11px; }}
     }}
 
     .chips {{
@@ -171,36 +185,43 @@ def _build_docs_html(*, base_url: str) -> str:
       border: 1px solid var(--border);
       background: var(--card-2);
       font-size: 12px;
-      color: rgba(255,255,255,0.85);
+      color: rgba(43, 29, 22, 0.86);
       white-space: nowrap;
     }}
-    .chip strong {{ color: rgba(255,255,255,0.94); }}
+    .chip strong {{ color: rgba(43, 29, 22, 0.94); }}
 
+    .table-wrap {{
+      overflow-x: auto;
+      -webkit-overflow-scrolling: touch;
+      border-radius: 12px;
+      border: 1px solid var(--border);
+      margin-top: 10px;
+      background: var(--card-2);
+    }}
     table {{
       width: 100%;
       border-collapse: collapse;
-      margin-top: 10px;
-      border-radius: 12px;
-      overflow: hidden;
-      border: 1px solid var(--border);
+      min-width: 680px;
     }}
     th, td {{
       padding: 10px 10px;
-      border-bottom: 1px solid rgba(255,255,255,0.10);
+      border-bottom: 1px solid rgba(58, 38, 26, 0.10);
       vertical-align: top;
       font-size: 13px;
       line-height: 1.45;
+      word-break: break-word;
     }}
     th {{
       text-align: left;
-      background: rgba(255,255,255,0.06);
-      color: rgba(255,255,255,0.92);
+      background: rgba(43, 29, 22, 0.04);
+      color: rgba(43, 29, 22, 0.92);
       font-weight: 600;
     }}
     td code {{
       font-family: var(--mono);
       font-size: 12px;
-      color: rgba(255,255,255,0.9);
+      color: rgba(43, 29, 22, 0.92);
+      word-break: break-all;
     }}
     .muted {{ color: var(--muted2); }}
     .note {{
@@ -208,10 +229,10 @@ def _build_docs_html(*, base_url: str) -> str:
       padding: 12px 12px;
       border-radius: 12px;
       border: 1px solid var(--border);
-      background: rgba(251, 191, 36, 0.10);
-      color: rgba(255,255,255,0.90);
+      background: rgba(180, 83, 9, 0.10);
+      color: rgba(43, 29, 22, 0.92);
     }}
-    .note strong {{ color: rgba(255,255,255,0.95); }}
+    .note strong {{ color: rgba(43, 29, 22, 0.95); }}
     .footer {{
       margin-top: 18px;
       color: var(--muted2);
@@ -273,14 +294,15 @@ def _build_docs_html(*, base_url: str) -> str:
 
     <section class="card" style="margin-top: 14px;">
       <h2>筛选语法速记</h2>
-      <table>
-        <thead>
-          <tr>
-            <th style="width: 170px;">参数</th>
-            <th>说明</th>
-          </tr>
-        </thead>
-        <tbody>
+      <div class="table-wrap" role="region" aria-label="filters-table" tabindex="0">
+        <table>
+          <thead>
+            <tr>
+              <th style="width: 170px;">参数</th>
+              <th>说明</th>
+            </tr>
+          </thead>
+          <tbody>
           <tr>
             <td><code>strategy</code></td>
             <td>
@@ -293,6 +315,7 @@ def _build_docs_html(*, base_url: str) -> str:
             <td>
               <code>0</code>/<code>1</code>：强制使用第三方反向代理拉取图片上游（即使全局未开启）。<br/>
               <span class="muted">上游可为 i.pixiv.cat / i.pixiv.re / i.pixiv.nl。</span><br/>
+              <span class="muted">未指定 pximg_mirror_host 时：大陆访问优先 i.pixiv.re，非大陆默认 i.pixiv.cat。</span><br/>
               <span class="muted">仅影响服务端拉图的上游域名，客户端仍访问本站域名。</span>
             </td>
           </tr>
@@ -354,8 +377,9 @@ def _build_docs_html(*, base_url: str) -> str:
             <td><code>attempts</code></td>
             <td>上游失败时重试次数（1–10）。</td>
           </tr>
-        </tbody>
-      </table>
+          </tbody>
+        </table>
+      </div>
       <div class="footer">
         其它接口：<a href="{examples["tags_api"]}">/tags</a>（标签列表）、<a href="{examples["authors_api"]}">/authors</a>（作者列表）。<br/>
         OpenAPI：<a href="{examples["openapi"]}">/openapi.json</a>，Swagger：<a href="{examples["swagger"]}">/api/docs</a>。<br/>
diff --git a/backend/app/api/public/images.py b/backend/app/api/public/images.py
index 111bd5b..4895333 100644
--- a/backend/app/api/public/images.py
+++ b/backend/app/api/public/images.py
@@ -12,7 +12,11 @@ from app.core.http_stream import stream_url
 import sqlalchemy as sa
 
 from app.core.pixiv_urls import ALLOWED_IMAGE_EXTS
-from app.core.pximg_reverse_proxy import normalize_pximg_mirror_host, rewrite_pximg_to_mirror
+from app.core.pximg_reverse_proxy import (
+    normalize_pximg_mirror_host,
+    pick_pximg_mirror_host_for_request,
+    rewrite_pximg_to_mirror,
+)
 from app.core.request_id import get_or_create_request_id, set_request_id_header, set_request_id_on_state
 from app.core.runtime_settings import load_runtime_config
 from app.core.time import iso_utc_ms
@@ -304,7 +308,12 @@ async def proxy_image(
 
     runtime = await load_runtime_config(engine)
     use_pixiv_cat = bool(runtime.image_proxy_use_pixiv_cat) or int(pixiv_cat) == 1
-    mirror_host = mirror_host_override or str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    runtime_mirror_host = str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    mirror_host = mirror_host_override or (
+        pick_pximg_mirror_host_for_request(headers=request.headers, fallback_host=runtime_mirror_host)
+        if use_pixiv_cat
+        else runtime_mirror_host
+    )
 
     async def _best_effort(fn, *args, timeout_s: float = 1.5, **kwargs) -> None:  # type: ignore[no-untyped-def]
         try:
diff --git a/backend/app/api/public/legacy.py b/backend/app/api/public/legacy.py
index 8ab1ab7..c2862cb 100644
--- a/backend/app/api/public/legacy.py
+++ b/backend/app/api/public/legacy.py
@@ -5,7 +5,11 @@ from fastapi import APIRouter, Request
 from app.core.errors import ApiError, ErrorCode
 from app.core.http_stream import stream_url
 from app.core.pixiv_urls import ALLOWED_IMAGE_EXTS
-from app.core.pximg_reverse_proxy import normalize_pximg_mirror_host, rewrite_pximg_to_mirror
+from app.core.pximg_reverse_proxy import (
+    normalize_pximg_mirror_host,
+    pick_pximg_mirror_host_for_request,
+    rewrite_pximg_to_mirror,
+)
 from app.core.proxy_routing import select_proxy_uri_for_url
 from app.core.runtime_settings import load_runtime_config
 from app.db.images_get_by_illust import get_image_by_illust_page
@@ -52,7 +56,12 @@ async def legacy_multi(
 
     runtime = await load_runtime_config(engine)
     use_pixiv_cat = bool(runtime.image_proxy_use_pixiv_cat) or int(pixiv_cat) == 1
-    mirror_host = mirror_host_override or str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    runtime_mirror_host = str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    mirror_host = mirror_host_override or (
+        pick_pximg_mirror_host_for_request(headers=request.headers, fallback_host=runtime_mirror_host)
+        if use_pixiv_cat
+        else runtime_mirror_host
+    )
     proxy_uri = None
     source_url = rewrite_pximg_to_mirror(str(image.original_url), mirror_host=mirror_host) if use_pixiv_cat else str(image.original_url)
     if not use_pixiv_cat:
@@ -110,7 +119,12 @@ async def legacy_single(
 
     runtime = await load_runtime_config(engine)
     use_pixiv_cat = bool(runtime.image_proxy_use_pixiv_cat) or int(pixiv_cat) == 1
-    mirror_host = mirror_host_override or str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    runtime_mirror_host = str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    mirror_host = mirror_host_override or (
+        pick_pximg_mirror_host_for_request(headers=request.headers, fallback_host=runtime_mirror_host)
+        if use_pixiv_cat
+        else runtime_mirror_host
+    )
     proxy_uri = None
     source_url = rewrite_pximg_to_mirror(str(image.original_url), mirror_host=mirror_host) if use_pixiv_cat else str(image.original_url)
     if not use_pixiv_cat:
diff --git a/backend/app/api/public/random.py b/backend/app/api/public/random.py
index fa50aa6..977e703 100644
--- a/backend/app/api/public/random.py
+++ b/backend/app/api/public/random.py
@@ -13,7 +13,11 @@ from fastapi.responses import RedirectResponse
 from app.core.errors import ApiError, ErrorCode
 from app.core.http_stream import stream_url
 from app.core.imgproxy import build_signed_processing_url, load_imgproxy_config_from_settings
-from app.core.pximg_reverse_proxy import normalize_pximg_mirror_host, rewrite_pximg_to_mirror
+from app.core.pximg_reverse_proxy import (
+    normalize_pximg_mirror_host,
+    pick_pximg_mirror_host_for_request,
+    rewrite_pximg_to_mirror,
+)
 from app.core.proxy_routing import select_proxy_uri_for_url
 from app.core.runtime_settings import load_runtime_config
 from app.core.time import iso_utc_ms
@@ -349,7 +353,12 @@ async def random_image(
     Session = create_sessionmaker(engine)
     runtime = await load_runtime_config(engine)
     use_pixiv_cat = bool(runtime.image_proxy_use_pixiv_cat) or int(pixiv_cat) == 1
-    mirror_host = mirror_host_override or str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    runtime_mirror_host = str(getattr(runtime, "image_proxy_pximg_mirror_host", "") or "").strip() or "i.pixiv.cat"
+    mirror_host = mirror_host_override or (
+        pick_pximg_mirror_host_for_request(headers=request.headers, fallback_host=runtime_mirror_host)
+        if use_pixiv_cat
+        else runtime_mirror_host
+    )
 
     async def _best_effort(fn, *args, timeout_s: float = 1.5, **kwargs) -> None:  # type: ignore[no-untyped-def]
         try:
diff --git a/backend/app/core/pximg_reverse_proxy.py b/backend/app/core/pximg_reverse_proxy.py
index a0c7ec2..9011501 100644
--- a/backend/app/core/pximg_reverse_proxy.py
+++ b/backend/app/core/pximg_reverse_proxy.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from collections.abc import Mapping
 from urllib.parse import urlparse, urlunparse
 
 
@@ -27,6 +28,71 @@ _PXIMG_MIRROR_ALIASES: dict[str, str] = {
 }
 
 
+_REQUEST_COUNTRY_HEADERS: tuple[str, ...] = (
+    # Cloudflare
+    "cf-ipcountry",
+    # Vercel
+    "x-vercel-ip-country",
+    # AWS CloudFront
+    "cloudfront-viewer-country",
+    # Google App Engine / GCP
+    "x-appengine-country",
+    # Common self-managed reverse proxies
+    "x-country-code",
+    "x-geo-country",
+)
+
+
+def _get_request_country_code(headers: Mapping[str, str] | None) -> str | None:
+    if not headers:
+        return None
+    lowered: dict[str, str] = {}
+    try:
+        for k, v in headers.items():
+            key = str(k or "").strip().lower()
+            if not key:
+                continue
+            val = str(v or "").strip()
+            if not val:
+                continue
+            lowered[key] = val
+    except Exception:
+        return None
+
+    for key in _REQUEST_COUNTRY_HEADERS:
+        val = lowered.get(key)
+        if not val:
+            continue
+        code = val.strip().upper()
+        if not code:
+            continue
+        # Some CDNs may return "CN,..." or other variants; we only need the first token.
+        code = code.split(",", 1)[0].strip()
+        if len(code) >= 2:
+            return code[:2]
+    return None
+
+
+def pick_pximg_mirror_host_for_request(
+    *,
+    headers: Mapping[str, str] | None,
+    fallback_host: str | None,
+) -> str:
+    """
+    Pick the best pximg mirror host for a request.
+
+    - If request is detected as mainland China, prefer i.pixiv.re (commonly faster inside CN).
+    - Otherwise use the configured fallback host (defaults to i.pixiv.cat).
+
+    Detection is best-effort and relies on CDN/reverse-proxy injected country headers
+    (e.g. Cloudflare's CF-IPCountry). If missing, falls back to the configured host.
+    """
+    fallback = normalize_pximg_mirror_host(fallback_host) or DEFAULT_PXIMG_MIRROR_HOST
+    if _get_request_country_code(headers) == "CN":
+        return "i.pixiv.re"
+    return fallback
+
+
 def is_pximg_image_url(url: str) -> bool:
     try:
         parsed = urlparse(url)
diff --git a/backend/app/db/engine.py b/backend/app/db/engine.py
index 1e933e8..f3e5295 100644
--- a/backend/app/db/engine.py
+++ b/backend/app/db/engine.py
@@ -11,10 +11,13 @@ from sqlalchemy.ext.asyncio import AsyncEngine, create_async_engine
 # legitimately hold the SQLite writer lock for several seconds. A higher default
 # busy timeout makes the system much more resilient under load (still overrideable
 # via SQLITE_BUSY_TIMEOUT_MS env).
-SQLITE_BUSY_TIMEOUT_MS = 30_000
-SQLITE_POOL_SIZE = 10
-SQLITE_MAX_OVERFLOW = 10
-SQLITE_POOL_TIMEOUT_S = 5
+#
+# NOTE: These defaults favor availability on reasonably powerful servers. For
+# smaller instances you may want to lower pool sizes and/or busy timeout.
+SQLITE_BUSY_TIMEOUT_MS = 60_000
+SQLITE_POOL_SIZE = 30
+SQLITE_MAX_OVERFLOW = 30
+SQLITE_POOL_TIMEOUT_S = 30
 
 
 def apply_sqlite_pragmas(dbapi_connection: Any) -> None:
diff --git a/backend/app/db/session.py b/backend/app/db/session.py
index b1fe7d5..54df48d 100644
--- a/backend/app/db/session.py
+++ b/backend/app/db/session.py
@@ -33,7 +33,7 @@ def is_sqlite_busy_error(exc: BaseException) -> bool:
 async def with_sqlite_busy_retry(
     op: Callable[[], Awaitable[T]],
     *,
-    retries: int = 8,
+    retries: int = 12,
     base_delay_s: float = 0.05,
 ) -> T:
     try:
@@ -49,9 +49,9 @@ async def with_sqlite_busy_retry(
     base_delay = float(max(0.0, min(float(env_base), 5.0)))
 
     try:
-        env_max_delay = float((os.environ.get("SQLITE_BUSY_MAX_DELAY_S") or "").strip() or 2.0)
+        env_max_delay = float((os.environ.get("SQLITE_BUSY_MAX_DELAY_S") or "").strip() or 5.0)
     except Exception:
-        env_max_delay = 2.0
+        env_max_delay = 5.0
     max_delay = float(max(0.0, min(float(env_max_delay), 30.0)))
 
     attempt = 0
diff --git a/backend/app/worker.py b/backend/app/worker.py
index 426d62f..4fdf522 100644
--- a/backend/app/worker.py
+++ b/backend/app/worker.py
@@ -350,7 +350,7 @@ async def main_async(*, max_iterations: int | None = None, poll_interval_s: floa
         )
         max_concurrency = _parse_int_env(
             "WORKER_MAX_CONCURRENCY",
-            default=20,
+            default=50,
             min_v=1,
             max_v=200,
         )
diff --git a/backend/tests/test_pximg_reverse_proxy.py b/backend/tests/test_pximg_reverse_proxy.py
new file mode 100644
index 0000000..5ad7e52
--- /dev/null
+++ b/backend/tests/test_pximg_reverse_proxy.py
@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+from app.core.pximg_reverse_proxy import pick_pximg_mirror_host_for_request
+
+
+def test_pick_pximg_mirror_host_for_request_prefers_re_for_cn() -> None:
+    host = pick_pximg_mirror_host_for_request(headers={"CF-IPCountry": "CN"}, fallback_host="i.pixiv.cat")
+    assert host == "i.pixiv.re"
+
+
+def test_pick_pximg_mirror_host_for_request_uses_fallback_for_non_cn() -> None:
+    host = pick_pximg_mirror_host_for_request(headers={"CF-IPCountry": "US"}, fallback_host="i.pixiv.nl")
+    assert host == "i.pixiv.nl"
+
+
+def test_pick_pximg_mirror_host_for_request_falls_back_to_default_on_invalid_fallback() -> None:
+    host = pick_pximg_mirror_host_for_request(headers=None, fallback_host="not-a-host")
+    assert host == "i.pixiv.cat"
+
diff --git a/deploy/.env.example b/deploy/.env.example
index 2e72616..2247221 100644
--- a/deploy/.env.example
+++ b/deploy/.env.example
@@ -12,7 +12,7 @@ WORKER_AUTO_CONCURRENCY=true
 # 自动并发刷新频率（秒）：token 数变化后多久生效
 WORKER_AUTO_CONCURRENCY_REFRESH_SECONDS=15
 # 并发上限（无论 token 有多少都不会超过这个值）
-WORKER_MAX_CONCURRENCY=20
+WORKER_MAX_CONCURRENCY=50
 
 # Secrets (do NOT commit real values).
 SECRET_KEY=dev-secret-key-change-me