diff --git a/src/allotropy/allotrope/converter.py b/src/allotropy/allotrope/converter.py
index 60d15fe5a..3bff3f625 100644
--- a/src/allotropy/allotrope/converter.py
+++ b/src/allotropy/allotrope/converter.py
@@ -208,6 +208,15 @@ def unstructure(obj: Any) -> Any:
         return result
 
     if isinstance(obj, list):
+        # Fast-path: lists of primitives (e.g., data cube float arrays with millions
+        # of elements) pass through unchanged — return directly to avoid per-element
+        # function call overhead.
+        if obj:
+            first = obj[0]
+            if (
+                first is None or isinstance(first, int | float | str | bool)
+            ) and not isinstance(first, Enum):
+                return obj
         return [unstructure(item) for item in obj]
 
     if isinstance(obj, dict):
diff --git a/src/allotropy/allotrope/schemas.py b/src/allotropy/allotrope/schemas.py
index e7f81fd6d..83e441d3e 100644
--- a/src/allotropy/allotrope/schemas.py
+++ b/src/allotropy/allotrope/schemas.py
@@ -5,6 +5,7 @@
 from typing import Any
 
 import jsonschema
+from jsonschema import ValidationError
 
 from allotropy.allotrope.path_util import (
     get_full_schema_path,
@@ -23,6 +24,98 @@
 FORMAT_CHECKER.checkers.pop("uri-reference", None)
 
 
+# ---------------------------------------------------------------------------
+# Optimized array items validator
+# ---------------------------------------------------------------------------
+# Data cube arrays can contain millions of floats. The default jsonschema
+# items validator calls validator.descend() per element — extremely slow for
+# simple type-only schemas like {"type": "number"} or
+# {"anyOf": [{"type": "number"}, {"type": "null"}]}.
+# We detect these patterns and do a single bulk isinstance pass instead.
+
+_SIMPLE_TYPE_MAP: dict[str, tuple[tuple[type, ...], bool]] = {
+    "number": ((int, float), True),
+    "string": ((str,), False),
+    "boolean": ((bool,), False),
+    "integer": ((int,), True),
+    "null": ((type(None),), False),
+}
+
+
+def _extract_accepted_types(
+    items_schema: Any,
+) -> tuple[tuple[type, ...], bool] | None:
+    """If items_schema is a simple type-only check, return (accepted_types, exclude_bool)."""
+    if not isinstance(items_schema, dict):
+        return None
+
+    keys = set(items_schema.keys())
+
+    if keys == {"type"} and isinstance(items_schema["type"], str):
+        return _SIMPLE_TYPE_MAP.get(items_schema["type"])
+
+    if keys == {"anyOf"} and isinstance(items_schema["anyOf"], list):
+        combined: set[type] = set()
+        exclude_bool = False
+        for sub in items_schema["anyOf"]:
+            if not (
+                isinstance(sub, dict)
+                and set(sub.keys()) == {"type"}
+                and isinstance(sub["type"], str)
+            ):
+                return None
+            entry = _SIMPLE_TYPE_MAP.get(sub["type"])
+            if entry is None:
+                return None
+            combined.update(entry[0])
+            exclude_bool = exclude_bool or entry[1]
+        return (tuple(combined), exclude_bool)
+
+    return None
+
+
+_original_items = jsonschema.validators.Draft202012Validator.VALIDATORS["items"]
+
+
+def _fast_items_validator(
+    validator: Any, items_schema: Any, instance: Any, schema: Any
+) -> Any:
+    """items validator that bulk-checks homogeneous primitive arrays."""
+    if not validator.is_type(instance, "array"):
+        return
+
+    if schema.get("prefixItems") or not instance:
+        yield from _original_items(validator, items_schema, instance, schema)
+        return
+
+    if items_schema is False:
+        yield ValidationError(f"Expected at most 0 items, but found {len(instance)}")
+        return
+
+    type_info = _extract_accepted_types(items_schema)
+    if type_info is None:
+        yield from _original_items(validator, items_schema, instance, schema)
+        return
+
+    accepted_types, exclude_bool = type_info
+    if exclude_bool:
+        for i, v in enumerate(instance):
+            if isinstance(v, bool) or not isinstance(v, accepted_types):
+                yield from validator.descend(instance[i], items_schema, path=i)
+                return
+    else:
+        for i, v in enumerate(instance):
+            if not isinstance(v, accepted_types):
+                yield from validator.descend(instance[i], items_schema, path=i)
+                return
+
+
+FastDraft202012Validator = jsonschema.validators.extend(  # type: ignore[no-untyped-call]
+    jsonschema.validators.Draft202012Validator,
+    validators={"items": _fast_items_validator},
+)
+
+
 def get_schema(schema_path: Path) -> dict[str, Any]:
     with open(get_full_schema_path(schema_path), encoding=DEFAULT_ENCODING) as f:
         return json.load(f)  # type: ignore[no-any-return]
@@ -87,7 +180,7 @@ def validate_asm_schema(asm_dict: dict[str, Any]) -> None:
             referrer=schema,
             store=store,
         )
-        validator = jsonschema.validators.Draft202012Validator(
+        validator = FastDraft202012Validator(
             schema, resolver=resolver, format_checker=FORMAT_CHECKER
         )
         validator.validate(asm_dict)