perf: cache upstream sources lookup in pypi_proxy

backend/app/pypi_proxy.py

@@ -254,6 +254,62 @@ def _extract_pypi_version(filename: str) -> Optional[str]:
     return None
 
 
+async def _get_pypi_upstream_sources_cached(
+    db: Session,
+    cache: CacheService,
+) -> list[UpstreamSource]:
+    """
+    Get PyPI upstream sources with caching.
+
+    Sources are cached for cache_ttl_upstream seconds to avoid
+    repeated database queries on every request.
+    """
+    cache_key = "sources"
+
+    # Try cache first
+    cached = await cache.get(CacheCategory.UPSTREAM_SOURCES, cache_key, protocol="pypi")
+    if cached:
+        source_data = json.loads(cached.decode())
+        # Reconstruct UpstreamSource-like objects from cached data
+        # We cache just the essential fields needed for requests
+        return [type('CachedSource', (), d)() for d in source_data]
+
+    # Query database
+    db_sources = (
+        db.query(UpstreamSource)
+        .filter(UpstreamSource.source_type == "pypi", UpstreamSource.enabled == True)
+        .order_by(UpstreamSource.priority)
+        .all()
+    )
+
+    # Combine with env sources
+    env_sources = [s for s in get_env_upstream_sources() if s.source_type == "pypi"]
+    all_sources = list(db_sources) + list(env_sources)
+    all_sources = sorted(all_sources, key=lambda s: s.priority)
+
+    # Cache the essential fields
+    if all_sources and cache.enabled:
+        cache_data = [
+            {
+                "name": s.name,
+                "url": s.url,
+                "priority": s.priority,
+                "auth_type": getattr(s, "auth_type", "none"),
+                "username": getattr(s, "username", None),
+                "password": getattr(s, "password", None),
+            }
+            for s in all_sources
+        ]
+        await cache.set(
+            CacheCategory.UPSTREAM_SOURCES,
+            cache_key,
+            json.dumps(cache_data).encode(),
+            protocol="pypi",
+        )
+
+    return all_sources
+
+
 def _get_pypi_upstream_sources(db: Session) -> list[UpstreamSource]:
     """Get all enabled upstream sources configured for PyPI."""
     # Get database sources