user: avoid full metadata copy in ExtractFromGRPCRequest

user/grpc.go

@@ -8,13 +8,8 @@ import (
 // ExtractFromGRPCRequest extracts the user ID from the request metadata and returns
 // the user ID and a context with the user ID injected.
 func ExtractFromGRPCRequest(ctx context.Context) (string, context.Context, error) {
-	md, ok := metadata.FromIncomingContext(ctx)
-	if !ok {
-		return "", ctx, ErrNoOrgID
-	}
-
-	orgIDs, ok := md[lowerOrgIDHeaderName]
-	if !ok || len(orgIDs) != 1 {
+	orgIDs := metadata.ValueFromIncomingContext(ctx, lowerOrgIDHeaderName)
+	if len(orgIDs) != 1 {
 		return "", ctx, ErrNoOrgID
 	}
 

user/grpc_test.go

@@ -0,0 +1,31 @@
+package user
+
+import (
+	"context"
+	"testing"
+
+	"google.golang.org/grpc/metadata"
+)
+
+func BenchmarkExtractFromGRPCRequest(b *testing.B) {
+	// Simulate a realistic incoming context with multiple metadata keys
+	md := metadata.MD{
+		"content-type":         []string{"application/grpc"},
+		"user-agent":          []string{"grpc-go/1.71.2"},
+		"x-scope-orgid":      []string{"tenant-12345"},
+		"x-forwarded-for":    []string{"10.0.0.1"},
+		"x-request-id":       []string{"abc-def-ghi-jkl"},
+		"traceparent":        []string{"00-abcdef1234567890abcdef1234567890-1234567890abcdef-01"},
+		"grpc-accept-encoding": []string{"gzip"},
+		"authorization":      []string{"Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9..."},
+		"x-amz-date":         []string{"20260507T183000Z"},
+		"x-amz-security-token": []string{"FwoGZXIvYXdzEBYaDH..."},
+	}
+	ctx := metadata.NewIncomingContext(context.Background(), md)
+
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, _, _ = ExtractFromGRPCRequest(ctx)
+	}
+}