diff --git a/service/api/service.go b/service/api/service.go
index 9c043182..3266af25 100644
--- a/service/api/service.go
+++ b/service/api/service.go
@@ -110,7 +110,8 @@ func (s *serviceImpl) ApiV1WorkflowStartPost(
 		initCustomSAs = startOptions.SearchAttributes
 		initCustomDAs = startOptions.DataAttributes
 		if startOptions.HasWorkflowConfigOverride() {
-			workflowConfig = startOptions.GetWorkflowConfigOverride()
+			configOverride := startOptions.GetWorkflowConfigOverride()
+			overrideWorkflowConfig(configOverride, workflowConfig)
 		}
 
 		workflowAlreadyStartedOptions := startOptions.WorkflowAlreadyStartedOptions
@@ -192,6 +193,34 @@ func (s *serviceImpl) ApiV1WorkflowStartPost(
 	}, nil
 }
 
+func overrideWorkflowConfig(configOverride iwfidl.WorkflowConfig, workflowConfig iwfidl.WorkflowConfig) {
+	if configOverride.ExecutingStateIdMode == nil {
+		*workflowConfig.ExecutingStateIdMode = service.DefaultExecutingStateIdMode
+	} else {
+		workflowConfig.ExecutingStateIdMode = configOverride.ExecutingStateIdMode
+	}
+	if configOverride.ContinueAsNewThreshold == nil {
+		workflowConfig.ContinueAsNewThreshold = iwfidl.PtrInt32(service.DefaultContinueAsNewThreshold)
+	} else {
+		workflowConfig.ContinueAsNewThreshold = configOverride.ContinueAsNewThreshold
+	}
+	if configOverride.ContinueAsNewPageSizeInBytes == nil {
+		workflowConfig.ContinueAsNewPageSizeInBytes = iwfidl.PtrInt32(service.DefaultContinueAsNewPageSizeInBytes)
+	} else {
+		workflowConfig.ContinueAsNewPageSizeInBytes = configOverride.ContinueAsNewPageSizeInBytes
+	}
+	if configOverride.DisableSystemSearchAttribute == nil {
+		workflowConfig.DisableSystemSearchAttribute = iwfidl.PtrBool(false)
+	} else {
+		workflowConfig.DisableSystemSearchAttribute = configOverride.DisableSystemSearchAttribute
+	}
+	if configOverride.OptimizeActivity == nil {
+		workflowConfig.OptimizeActivity = iwfidl.PtrBool(false)
+	} else {
+		workflowConfig.OptimizeActivity = configOverride.OptimizeActivity
+	}
+}
+
 func (s *serviceImpl) ApiV1WorkflowWaitForStateCompletion(
 	ctx context.Context, req iwfidl.WorkflowWaitForStateCompletionRequest,
 ) (wresp *iwfidl.WorkflowWaitForStateCompletionResponse, retError *errors.ErrorAndStatus) {
diff --git a/service/const.go b/service/const.go
index a7014884..e2835ba2 100644
--- a/service/const.go
+++ b/service/const.go
@@ -1,5 +1,7 @@
 package service
 
+import "github.com/indeedeng/iwf/gen/iwfidl"
+
 type (
 	BackendType string
 )
@@ -7,7 +9,10 @@ type (
 const (
 	EnvNameDebugMode = "DEBUG_MODE"
 
+	// Defaults for WorkflowConfig excluding booleans
 	DefaultContinueAsNewPageSizeInBytes = 1024 * 1024
+	DefaultContinueAsNewThreshold       = 100
+	DefaultExecutingStateIdMode         = iwfidl.ENABLED_FOR_STATES_WITH_WAIT_UNTIL
 
 	// below are special unofficial code for special use case