diff --git a/app/api/sources.py b/app/api/sources.py
index c273680..f70d9c6 100644
--- a/app/api/sources.py
+++ b/app/api/sources.py
@@ -16,6 +16,7 @@ from __future__ import annotations
 import logging
 import os
 import re
+import threading
 import time
 from datetime import datetime
 from pathlib import Path
@@ -27,7 +28,7 @@ from sqlalchemy import func, select
 from sqlalchemy.orm import Session
 
 from app.auth import require_api_key
-from app.db import get_session
+from app.db import get_session, session_scope
 from app.models.playback_source import PlaybackSource
 from app.models.source_stats import SourceStats
 
@@ -86,8 +87,10 @@ class SourceOut(BaseModel):
 
 
 _ICON_DIR = Path(__file__).resolve().parent.parent / "static" / "site-icons"
-_SOURCES_TTL = 300.0
+#: Po tylu sekundach wynik uznajemy za stary i przeliczamy W TLE (oddajac stary).
+_SOURCES_TTL = 900.0
 _SOURCES_CACHE: dict = {"at": 0.0, "rows": None}
+_SOURCES_LOCK = threading.Lock()
 
 
 def _icon_url(sitetag: str) -> str | None:
@@ -134,6 +137,50 @@ def _sitetag_to_display(sitetag: str) -> str:
     return sitetag
 
 
+def _source_rows(session: Session):
+    return session.execute(
+        select(
+            PlaybackSource.origin,
+            func.count(PlaybackSource.id).label("scene_count"),
+            func.max(PlaybackSource.last_seen_at).label("last_scraped_at"),
+        )
+        .where(PlaybackSource.dead_at.is_(None))
+        .where(PlaybackSource.origin.like("tube:%"))
+        .group_by(PlaybackSource.origin)
+    ).all()
+
+
+def _refresh_source_rows_bg() -> None:
+    if not _SOURCES_LOCK.acquire(blocking=False):
+        return  # ktos juz liczy
+
+    def run() -> None:
+        try:
+            with session_scope() as s:
+                rows = _source_rows(s)
+            _SOURCES_CACHE["rows"] = rows
+            _SOURCES_CACHE["at"] = time.monotonic()
+        except Exception:  # noqa: BLE001
+            log.exception("sources: odswiezenie listy stron w tle nie wyszlo")
+        finally:
+            _SOURCES_LOCK.release()
+
+    threading.Thread(target=run, name="sources-refresh", daemon=True).start()
+
+
+def _cached_source_rows(session: Session):
+    rows = _SOURCES_CACHE["rows"]
+    if rows is None:
+        with _SOURCES_LOCK:
+            if _SOURCES_CACHE["rows"] is None:
+                _SOURCES_CACHE["rows"] = _source_rows(session)
+                _SOURCES_CACHE["at"] = time.monotonic()
+        return _SOURCES_CACHE["rows"]
+    if time.monotonic() - _SOURCES_CACHE["at"] > _SOURCES_TTL:
+        _refresh_source_rows_bg()
+    return rows
+
+
 @router.get("", response_model=SourceListOut)
 def list_sources(
     session: Annotated[Session, Depends(get_session)],
@@ -142,23 +189,11 @@ def list_sources(
 
     Filter: `origin LIKE 'tube:%'` (drop canonical:* TPDB trailery to inna semantyka).
     """
-    # Agregat idzie po 4,1 mln zywych zrodel (600 ms na kazde wejscie w Sites, Sentry:
-    # Slow DB Query list_sources). Liczby zmieniaja sie o promile na godzine, wiec
-    # wynik zyje w pamieci procesu przez _SOURCES_TTL sekund.
-    now = time.monotonic()
-    if _SOURCES_CACHE["rows"] is None or now - _SOURCES_CACHE["at"] > _SOURCES_TTL:
-        _SOURCES_CACHE["rows"] = session.execute(
-            select(
-                PlaybackSource.origin,
-                func.count(PlaybackSource.id).label("scene_count"),
-                func.max(PlaybackSource.last_seen_at).label("last_scraped_at"),
-            )
-            .where(PlaybackSource.dead_at.is_(None))
-            .where(PlaybackSource.origin.like("tube:%"))
-            .group_by(PlaybackSource.origin)
-        ).all()
-        _SOURCES_CACHE["at"] = now
-    rows = _SOURCES_CACHE["rows"]
+    # Agregat idzie po 4,1 mln zywych zrodel (0,6-1,6 s na przeliczenie, Sentry: Slow DB
+    # Query list_sources, 186 zdarzen). Liczby zmieniaja sie o promile na godzine, wiec
+    # wynik zyje w pamieci procesu, a po wygasnieciu oddajemy STARY i przeliczamy w tle.
+    # Wczesniej co wygasniecie cache ktos placil pelnym czasem zapytania (2026-09-17).
+    rows = _cached_source_rows(session)
 
     # Oceny z source_stats (policzone offline przez run_source_stats). Origin → row.
     stats = {s.origin: s for s in session.execute(select(SourceStats)).scalars().all()}