diff --git a/guardrails/validator_service/__init__.py b/guardrails/validator_service/__init__.py
index 0bb2f8b89..7139603e0 100644
--- a/guardrails/validator_service/__init__.py
+++ b/guardrails/validator_service/__init__.py
@@ -29,6 +29,9 @@
 
 def should_run_sync():
     process_count = os.environ.get("GUARDRAILS_PROCESS_COUNT")
+    # Short-circuit for 'GUARDRAILS_RUN_SYNC', and avoid duplicate lower() & lookups
+    run_sync = os.environ.get("GUARDRAILS_RUN_SYNC", "false")
+    run_sync_lower = run_sync.lower()
     if process_count is not None:
         warnings.warn(
             "GUARDRAILS_PROCESS_COUNT is deprecated"
@@ -37,13 +40,15 @@ def should_run_sync():
             DeprecationWarning,
         )
         process_count = int(process_count)
-    run_sync = os.environ.get("GUARDRAILS_RUN_SYNC", "false")
-    bool_values = ["true", "false"]
-    if run_sync.lower() not in bool_values:
+        # If process_count == 1, immediately return True for efficiency
+        if process_count == 1:
+            return True
+    # Avoid reconstructing list for each call
+    if run_sync_lower not in ("true", "false"):
         warnings.warn(
-            f"GUARDRAILS_RUN_SYNC must be one of {bool_values}! Defaulting to 'false'."
+            "GUARDRAILS_RUN_SYNC must be one of ['true', 'false']! Defaulting to 'false'."
         )
-    return process_count == 1 or run_sync.lower() == "true"
+    return run_sync_lower == "true"
 
 
 def get_loop() -> asyncio.AbstractEventLoop: