diff --git a/pkg/operator/api/userconfig/apis.go b/pkg/operator/api/userconfig/apis.go
index 3421c9f742..a7b5a79490 100644
--- a/pkg/operator/api/userconfig/apis.go
+++ b/pkg/operator/api/userconfig/apis.go
@@ -206,9 +206,9 @@ func (api *API) UserConfigStr() string {
 	return sb.String()
 }
 
-func (apis APIs) Validate() error {
+func (apis APIs) Validate(projectFileMap map[string][]byte) error {
 	for _, api := range apis {
-		if err := api.Validate(); err != nil {
+		if err := api.Validate(projectFileMap); err != nil {
 			return err
 		}
 	}
@@ -226,7 +226,7 @@ func (apis APIs) Validate() error {
 	return nil
 }
 
-func (api *API) Validate() error {
+func (api *API) Validate(projectFileMap map[string][]byte) error {
 	awsClient, err := aws.NewFromS3Path(api.Model, false)
 	if err != nil {
 		return err
@@ -269,6 +269,12 @@ func (api *API) Validate() error {
 		return errors.Wrap(ErrorTFServingOptionsForTFOnly(api.ModelFormat), Identify(api))
 	}
 
+	if api.RequestHandler != nil {
+		if _, ok := projectFileMap[*api.RequestHandler]; !ok {
+			return errors.Wrap(ErrorImplDoesNotExist(*api.RequestHandler), Identify(api), RequestHandlerKey)
+		}
+	}
+
 	if err := api.Compute.Validate(); err != nil {
 		return errors.Wrap(err, Identify(api), ComputeKey)
 	}
diff --git a/pkg/operator/api/userconfig/config.go b/pkg/operator/api/userconfig/config.go
index 6b5f3d158c..2be02c1a0c 100644
--- a/pkg/operator/api/userconfig/config.go
+++ b/pkg/operator/api/userconfig/config.go
@@ -22,6 +22,7 @@ import (
 	cr "github.com/cortexlabs/cortex/pkg/lib/configreader"
 	"github.com/cortexlabs/cortex/pkg/lib/errors"
 	"github.com/cortexlabs/cortex/pkg/lib/files"
+	"github.com/cortexlabs/cortex/pkg/lib/zip"
 	"github.com/cortexlabs/cortex/pkg/operator/api/resource"
 )
 
@@ -35,13 +36,18 @@ var typeFieldValidation = &cr.StructFieldValidation{
 	Nil: true,
 }
 
-func (config *Config) Validate() error {
+func (config *Config) Validate(projectBytes []byte) error {
 	if err := config.App.Validate(); err != nil {
 		return err
 	}
 
+	projectFileMap, err := zip.UnzipMemToMem(projectBytes)
+	if err != nil {
+		return err
+	}
+
 	if config.APIs != nil {
-		if err := config.APIs.Validate(); err != nil {
+		if err := config.APIs.Validate(projectFileMap); err != nil {
 			return err
 		}
 	}
@@ -49,7 +55,7 @@ func (config *Config) Validate() error {
 	return nil
 }
 
-func New(filePath string, configBytes []byte, validate bool) (*Config, error) {
+func New(filePath string, configBytes []byte) (*Config, error) {
 	var err error
 
 	configData, err := cr.ReadYAMLBytes(configBytes)
@@ -109,11 +115,6 @@ func New(filePath string, configBytes []byte, validate bool) (*Config, error) {
 		return nil, ErrorMissingAppDefinition()
 	}
 
-	if validate {
-		if err := config.Validate(); err != nil {
-			return nil, err
-		}
-	}
 	return config, nil
 }
 
@@ -123,7 +124,7 @@ func ReadAppName(filePath string, relativePath string) (string, error) {
 		return "", errors.Wrap(err, relativePath, ErrorReadConfig().Error())
 	}
 
-	config, err := New(relativePath, configBytes, false)
+	config, err := New(relativePath, configBytes)
 	if err != nil {
 		return "", err
 	}
diff --git a/pkg/operator/context/apis.go b/pkg/operator/context/apis.go
index 1cb0c1698b..5af9f79dd4 100644
--- a/pkg/operator/context/apis.go
+++ b/pkg/operator/context/apis.go
@@ -36,9 +36,13 @@ func getAPIs(config *userconfig.Config, deploymentVersion string, projectID stri
 		buf.WriteString(s.Obj(apiConfig.Tracker))
 		buf.WriteString(apiConfig.ModelFormat.String())
 		buf.WriteString(deploymentVersion)
-		buf.WriteString(projectID)
 		buf.WriteString(strings.TrimSuffix(apiConfig.Model, "/"))
 
+		if apiConfig.RequestHandler != nil {
+			buf.WriteString(projectID)
+			buf.WriteString(*apiConfig.RequestHandler)
+		}
+
 		id := hash.Bytes(buf.Bytes())
 
 		apis[apiConfig.Name] = &context.API{
diff --git a/pkg/operator/context/context.go b/pkg/operator/context/context.go
index 0ecc1dd0ce..d145f5dfd7 100644
--- a/pkg/operator/context/context.go
+++ b/pkg/operator/context/context.go
@@ -60,6 +60,7 @@ func New(
 	)
 
 	ctx.ProjectID = hash.Bytes(projectBytes)
+
 	ctx.ProjectKey = filepath.Join(consts.ProjectsDir, ctx.ProjectID+".zip")
 	if err = config.AWS.UploadBytesToS3(projectBytes, ctx.ProjectKey); err != nil {
 		return nil, err
diff --git a/pkg/operator/endpoints/deploy.go b/pkg/operator/endpoints/deploy.go
index 00d3279916..9dda4cbe5a 100644
--- a/pkg/operator/endpoints/deploy.go
+++ b/pkg/operator/endpoints/deploy.go
@@ -47,15 +47,21 @@ func Deploy(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	userconf, err := userconfig.New("cortex.yaml", configBytes, true)
+	projectBytes, err := files.ReadReqFile(r, "project.zip")
+	if err != nil {
+		RespondError(w, errors.WithStack(err))
+		return
+	}
+
+	userconf, err := userconfig.New("cortex.yaml", configBytes)
 	if err != nil {
 		RespondError(w, err)
 		return
 	}
 
-	projectBytes, err := files.ReadReqFile(r, "project.zip")
+	err = userconf.Validate(projectBytes)
 	if err != nil {
-		RespondError(w, errors.WithStack(err))
+		RespondError(w, err)
 		return
 	}