diff --git a/eth_utils/applicators.py b/eth_utils/applicators.py
index 9bfd5939..5cb3e91f 100644
--- a/eth_utils/applicators.py
+++ b/eth_utils/applicators.py
@@ -28,18 +28,19 @@
 
 @return_arg_type(2)
 def apply_formatter_at_index(
-    formatter: Callable[..., Any], at_index: int, value: List[Any]
-) -> Generator[List[Any], None, None]:
-    if at_index + 1 > len(value):
+    formatter: Callable[..., Any], at_index: int, value: Sequence[Any]
+) -> Generator[Any, None, None]:
+    try:
+        item = value[at_index]
+    except IndexError:
         raise IndexError(
             f"Not enough values in iterable to apply formatter. Got: {len(value)}. "
             f"Need: {at_index + 1}"
-        )
-    for index, item in enumerate(value):
-        if index == at_index:
-            yield formatter(item)
-        else:
-            yield item
+        ) from None
+
+    yield from value[:at_index]
+    yield formatter(item)
+    yield from value[at_index + 1 :]
 
 
 def combine_argument_formatters(*formatters: List[Callable[..., Any]]) -> Formatters:
diff --git a/newsfragments/306.performance.rst b/newsfragments/306.performance.rst
new file mode 100644
index 00000000..1b08a297
--- /dev/null
+++ b/newsfragments/306.performance.rst
@@ -0,0 +1 @@
+optimize apply_formatter_at_index