diff --git a/conda_build/metadata.py b/conda_build/metadata.py
index 01f3367d03..60922b438c 100644
--- a/conda_build/metadata.py
+++ b/conda_build/metadata.py
@@ -281,8 +281,8 @@ def select_lines(data, namespace, variants_in_place):
         if line.lstrip().startswith("#"):
             # Don't bother with comment only lines
             continue
-        m = sel_pat.match(line)
-        if m:
+        # Checking for "[" and "]" before regex matching every line is a bit faster.
+        if "[" in line and "]" in line and (m := sel_pat.match(line)):
             cond = m.group(3)
             try:
                 if eval_selector(cond, namespace, variants_in_place):
@@ -889,8 +889,8 @@ def get_output_dicts_from_metadata(metadata, outputs=None):
             outputs.append(OrderedDict(name=metadata.name()))
     for out in outputs:
         if (
-            "package:" in metadata.get_recipe_text()
-            and out.get("name") == metadata.name()
+            out.get("name") == metadata.name()
+            and "package:" in metadata.get_recipe_text()
         ):
             combine_top_level_metadata_with_output(metadata, out)
     return outputs
@@ -1015,6 +1015,7 @@ def get_updated_output_dict_from_reparsed_metadata(original_dict, new_outputs):
     return output_d
 
 
+@lru_cache(maxsize=200)
 def _filter_recipe_text(text, extract_pattern=None):
     if extract_pattern:
         match = re.search(extract_pattern, text, flags=re.MULTILINE | re.DOTALL)
@@ -1665,7 +1666,6 @@ def build_id(self):
             raise RuntimeError(
                 f"Couldn't extract raw recipe text for {self.name()} output"
             )
-        raw_recipe_text = self.extract_package_and_build_text()
         raw_manual_build_string = re.search(r"\s*string:", raw_recipe_text)
         # user setting their own build string.  Don't modify it.
         if manual_build_string and not (
@@ -2641,13 +2641,11 @@ def get_loop_vars(self):
         return variants.get_vars(_variants, loop_only=True)
 
     def get_used_loop_vars(self, force_top_level=False, force_global=False):
-        return {
-            var
-            for var in self.get_used_vars(
-                force_top_level=force_top_level, force_global=force_global
-            )
-            if var in self.get_loop_vars()
-        }
+        loop_vars = self.get_loop_vars()
+        used_vars = self.get_used_vars(
+            force_top_level=force_top_level, force_global=force_global
+        )
+        return set(loop_vars).intersection(used_vars)
 
     def get_rendered_recipe_text(
         self, permit_undefined_jinja=False, extract_pattern=None
diff --git a/conda_build/variants.py b/conda_build/variants.py
index c5bbe9a41e..076309fa4c 100644
--- a/conda_build/variants.py
+++ b/conda_build/variants.py
@@ -697,16 +697,18 @@ def get_package_variants(recipedir_or_metadata, config=None, variants=None):
 def get_vars(variants, loop_only=False):
     """For purposes of naming/identifying, provide a way of identifying which variables contribute
     to the matrix dimensionality"""
-    special_keys = {"pin_run_as_build", "zip_keys", "ignore_version"}
-    special_keys.update(set(ensure_list(variants[0].get("extend_keys"))))
+    first_variant, *other_variants = variants
+    special_keys = {
+        "pin_run_as_build",
+        "zip_keys",
+        "ignore_version",
+        *ensure_list(first_variant.get("extend_keys")),
+    }
     loop_vars = [
         k
-        for k in variants[0]
+        for k, v in first_variant.items()
         if k not in special_keys
-        and (
-            not loop_only
-            or any(variant[k] != variants[0][k] for variant in variants[1:])
-        )
+        and (not loop_only or any(variant[k] != v for variant in other_variants))
     ]
     return loop_vars
 
@@ -763,7 +765,9 @@ def find_used_variables_in_shell_script(variant, file_path):
         text = f.read()
     used_variables = set()
     for v in variant:
-        variant_regex = r"(^[^$]*?\$\{?\s*%s\s*[\s|\}])" % v
+        if v not in text:
+            continue
+        variant_regex = rf"(^[^$]*?\$\{{?\s*{re.escape(v)}\s*[\s|\}}])"
         if re.search(variant_regex, text, flags=re.MULTILINE | re.DOTALL):
             used_variables.add(v)
     return used_variables
@@ -774,7 +778,9 @@ def find_used_variables_in_batch_script(variant, file_path):
         text = f.read()
     used_variables = set()
     for v in variant:
-        variant_regex = r"\%" + v + r"\%"
+        if v not in text:
+            continue
+        variant_regex = rf"\%{re.escape(v)}\%"
         if re.search(variant_regex, text, flags=re.MULTILINE | re.DOTALL):
             used_variables.add(v)
     return used_variables
diff --git a/news/5248-render-speedups-func-calls b/news/5248-render-speedups-func-calls
new file mode 100644
index 0000000000..77863ddf02
--- /dev/null
+++ b/news/5248-render-speedups-func-calls
@@ -0,0 +1,19 @@
+### Enhancements
+
+* Speed up rendering by avoiding costly/redundant function calls. (#5248)
+
+### Bug fixes
+
+* <news item>
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* <news item>
+
+### Other
+
+* <news item>