diff --git a/backend/app/services/document_metadata_service.py b/backend/app/services/document_metadata_service.py
index b334933..3e82659 100644
--- a/backend/app/services/document_metadata_service.py
+++ b/backend/app/services/document_metadata_service.py
@@ -69,7 +69,9 @@ async def get_document(doc_id: str) -> dict | None:
         .maybe_single()
         .execute()
     )
-    return _normalize(result.data) if result.data else None
+    if result is None or not getattr(result, "data", None):
+        return None
+    return _normalize(result.data)
 
 
 async def update_document_stage(doc_id: str, stage: str) -> None:
diff --git a/backend/app/services/document_pipeline.py b/backend/app/services/document_pipeline.py
index 513c4aa..7a7b3a0 100644
--- a/backend/app/services/document_pipeline.py
+++ b/backend/app/services/document_pipeline.py
@@ -28,6 +28,12 @@
 _VALID_DOC_TYPES = {"RFQ", "PO", "CFG", "Client CSV", "Sales CSV"}
 _COGNEE_TIMEOUT = int(os.getenv("COGNEE_TIMEOUT_SECONDS", "300"))
 
+# Serialize run_pipeline() across concurrent uploads so we don't burst
+# past Gemini's per-minute embedding cap. One doc fully completes (or
+# fails) before the next pipeline starts. Upload response still returns
+# immediately; docs queue as status="processing".
+_PIPELINE_LOCK = asyncio.Lock()
+
 
 # ---------------------------------------------------------------------------
 # Helpers
@@ -108,7 +114,20 @@ async def run_pipeline(
     Progress stages written to DB:
         uploading → ingesting → building_graph → analyzing
         → extracting_insights → completed  (or failed)
+
+    Serialized via `_PIPELINE_LOCK`: if several uploads arrive at once,
+    each pipeline waits for the prior one to finish. Upload response still
+    returns immediately — docs queue as status="processing".
     """
+    async with _PIPELINE_LOCK:
+        await _run_pipeline_locked(file_path, doc_id, original_filename)
+
+
+async def _run_pipeline_locked(
+    file_path: Path,
+    doc_id: str,
+    original_filename: str,
+) -> None:
     sb = await get_async_supabase()
 
     async def _update(**fields) -> None:
diff --git a/backend/cortex_local.db b/backend/cortex_local.db
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index 77287f8..0000000
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diff --git a/backend/cortex_local.db-shm b/backend/cortex_local.db-shm
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diff --git a/backend/cortex_local.db-wal b/backend/cortex_local.db-wal
deleted file mode 100644
index e69de29..0000000