- cloud_cache.py: module-level TTLCache(maxsize=1000, ttl=60) singleton with
threading.Lock for concurrent access safety (RESEARCH.md Pattern 8 / D-16)
- get_cloud_folders_cached(): async function; calls fetch_fn OUTSIDE the lock
to avoid blocking the event loop during cloud API calls
- invalidate_provider_cache(): removes all cache entries for a user+provider prefix
- storage/__init__.py: adds get_storage_backend_for_document() async factory
— returns MinIOBackend for minio docs; queries CloudConnection (scoped to user.id),
decrypts credentials, and lazy-imports cloud backends to avoid circular imports
— raises HTTPException(503) if connection missing or not ACTIVE (T-05-02-04)