diff --git a/materializationengine/celery_worker.py b/materializationengine/celery_worker.py
index bc097cff..7f1f9809 100644
--- a/materializationengine/celery_worker.py
+++ b/materializationengine/celery_worker.py
@@ -71,7 +71,7 @@ def create_celery(app=None):
             "result_expires": 86400,  # results expire in broker after 1 day
             "redis_socket_connect_timeout": 10,
             "broker_transport_options": {
-                "visibility_timeout": 8000,
+                "visibility_timeout": 21600,
                 "socket_timeout": 20,
                 "socket_connect_timeout": 20,
             },  # timeout (s) for tasks to be sent back to broker queue
diff --git a/materializationengine/config.py b/materializationengine/config.py
index 829fb54f..242df579 100644
--- a/materializationengine/config.py
+++ b/materializationengine/config.py
@@ -78,6 +78,9 @@ class BaseConfig:
         if "DELTALAKE_OPTIMIZE_TARGET_SIZE_BYTES" in os.environ
         else None
     )
+    # this one should help with memory during optimize if it is still a problem,
+    # but has not been tested on the mesh worker nodes. im not sure how spilling to 
+    # disk on those will work out of the box
     DELTALAKE_OPTIMIZE_MAX_SPILL_SIZE_BYTES = (
         int(os.environ["DELTALAKE_OPTIMIZE_MAX_SPILL_SIZE_BYTES"])
         if "DELTALAKE_OPTIMIZE_MAX_SPILL_SIZE_BYTES" in os.environ
diff --git a/materializationengine/workflows/deltalake_export.py b/materializationengine/workflows/deltalake_export.py
index 3ce74a0a..c7177ddd 100644
--- a/materializationengine/workflows/deltalake_export.py
+++ b/materializationengine/workflows/deltalake_export.py
@@ -246,7 +246,7 @@ def _spatial_col_rank(col_name: str) -> int:
     if spatial_candidates:
         spatial_candidates.sort(key=lambda c: _spatial_col_rank(c[0]))
         col, owning_table = spatial_candidates[0]
-        # Spatial index — partition on Morton code, z-order on coordinates
+        # Spatial index — partition on Morton code, z-order on Morton column
         # NOTE: using the uniform range approach here as the percentile approach
         # won't work without some extra tooling, as the morton column doesn't
         # exist in the db
@@ -255,7 +255,7 @@ def _spatial_col_rank(col_name: str) -> int:
                 partition_by=f"{col}_morton",
                 partition_strategy="uniform_range",
                 n_partitions="auto",
-                zorder_columns=[f"{col}_x", f"{col}_y", f"{col}_z"],
+                zorder_columns=[f"{col}_morton"],
                 bloom_filter_columns=[],
                 source_geometry_column=col,
                 source_table=owning_table,
@@ -1334,6 +1334,8 @@ def _build_frozen_db_connection_string(
     name="deltalake:write_deltalake_table",
     bind=True,
     acks_late=True,
+    soft_time_limit=21000,
+    time_limit=21300,
 )
 def write_deltalake_table(
     self,
@@ -1465,7 +1467,7 @@ def write_deltalake_table(
         )
         return
 
-    # --- Partial-export detection (task 8.4) ---
+    # --- Existing Delta Lake detection ---
     for spec in resolved_specs:
         lake_name = spec.partition_by or "flat"
         uri = f"{output_uri_base}/{lake_name}"
@@ -1489,17 +1491,10 @@ def write_deltalake_table(
             )
 
         if existing_rows is not None:
-            celery_logger.info(
-                "Existing Delta Lake found for table %s (v%d) at %s: "
-                "%d rows (expected %d)",
-                table_name,
-                version,
-                uri,
-                existing_rows,
-                row_count,
-            )
-            celery_logger.info(
-                "Assuming existing Delta Lake is correct and skipping export for this spec."
+            raise RuntimeError(
+                f"Delta Lake for table {table_name!r} already exists at "
+                f"{uri} with {existing_rows} rows (matches expected count). "
+                f"Delete the existing Delta Lake before re-exporting."
             )
 
     # --- Estimate bytes per row and resolve partition counts / bounds ---
diff --git a/tests/test_deltalake_export.py b/tests/test_deltalake_export.py
index 3a73a4aa..e78f9e89 100644
--- a/tests/test_deltalake_export.py
+++ b/tests/test_deltalake_export.py
@@ -108,11 +108,7 @@ def test_spatial_index_produces_morton_spec(self):
         assert len(specs) == 1
         assert specs[0].partition_by == "pt_position_morton"
         assert specs[0].partition_strategy == "uniform_range"
-        assert specs[0].zorder_columns == [
-            "pt_position_x",
-            "pt_position_y",
-            "pt_position_z",
-        ]
+        assert specs[0].zorder_columns == ["pt_position_morton"]
         assert specs[0].source_geometry_column == "pt_position"
 
     def test_multiple_indexes(self):