diff --git a/instance/conn_name.go b/instance/conn_name.go
index 0f9aec20..79120947 100644
--- a/instance/conn_name.go
+++ b/instance/conn_name.go
@@ -31,8 +31,7 @@ var (
 	// The domain name pattern in accordance with RFC 1035, RFC 1123 and RFC 2181.
 	domainNameRegex = regexp.MustCompile(`^(?:[_a-z0-9](?:[_a-z0-9-]{0,61}[a-z0-9])?\.)+(?:[a-z](?:[a-z0-9-]{0,61}[a-z0-9])?)?$`)
 
-	instanceDNSSuffixRegex = regexp.MustCompile(`\.sql(-[a-zA-Z0-9_]+)?\.goog\.?$`)
-	globalInstanceDNSRegex = regexp.MustCompile(`\.global\.sql(-[a-zA-Z0-9_]+)?\.goog\.?$`)
+	instanceDNSNamePattern = regexp.MustCompile(`^([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])\.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])\.([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])\.(sql|sql-psa|sql-psc)\.goog\.?$`)
 )
 
 // ConnName represents the "instance connection name", in the format
@@ -129,47 +128,20 @@ type ConnectionNameResolver interface {
 // Suffix is one of: sql.goog, sql-psa.goog, sql-psc.goog (with optional trailing dot).
 // This returns ok == false when the region is "global"
 func ParseInstanceDNSName(dnsName string) (instanceLabel, projectLabel, region, suffix string, ok bool) {
-	dnsName = strings.TrimSuffix(dnsName, ".")
 	dnsName = strings.ToLower(dnsName)
-
-	parts := strings.Split(dnsName, ".")
-	if len(parts) != 5 {
-		return "", "", "", "", false
-	}
-
-	if parts[4] != "goog" {
-		return "", "", "", "", false
-	}
-
-	suffixType := parts[3]
-	if suffixType != "sql" && suffixType != "sql-psa" && suffixType != "sql-psc" {
+	m := instanceDNSNamePattern.FindStringSubmatch(dnsName)
+	if m == nil {
 		return "", "", "", "", false
 	}
+	instanceLabel = m[1]
+	projectLabel = m[2]
+	region = m[3]
+	suffix = m[4] + ".goog"
 
-	instanceLabel = parts[0]
-	projectLabel = parts[1]
-	region = parts[2]
-	suffix = suffixType + ".goog"
-
-	// Validate region != "global". "global" is used for redirect to write endpoint DNS
 	if region == "global" {
 		return "", "", "", "", false
 	}
 
-	// Validate labels
-	if len(instanceLabel) != 12 {
-		return "", "", "", "", false
-	}
-	for _, c := range instanceLabel {
-		if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
-			return "", "", "", "", false
-		}
-	}
-
-	if !strings.Contains(region, "-") {
-		return "", "", "", "", false
-	}
-
 	return instanceLabel, projectLabel, region, suffix, true
 }
 
@@ -177,5 +149,9 @@ func ParseInstanceDNSName(dnsName string) (instanceLabel, projectLabel, region,
 // Cloud SQL instance DNS name pattern.
 func IsInstanceDNSName(dnsName string) bool {
 	dnsName = strings.ToLower(dnsName)
-	return instanceDNSSuffixRegex.MatchString(dnsName) && !globalInstanceDNSRegex.MatchString(dnsName)
+	m := instanceDNSNamePattern.FindStringSubmatch(dnsName)
+	if m == nil {
+		return false
+	}
+	return m[3] != "global"
 }
diff --git a/internal/cloudsql/resolver_test.go b/internal/cloudsql/resolver_test.go
index 9cb0da9b..fd5d4509 100644
--- a/internal/cloudsql/resolver_test.go
+++ b/internal/cloudsql/resolver_test.go
@@ -121,6 +121,34 @@ func TestDNSInstanceNameResolver_Lookup_Success_DirectPSC(t *testing.T) {
 	}
 }
 
+func TestDNSInstanceNameResolver_Lookup_Success_DirectPSC_Permissive(t *testing.T) {
+	// non-hex hash, short labels, region without hyphen
+	dnsName := "g123.p.uscentral.sql-psc.goog"
+	realConnName := "my-project:uscentral:my-instance"
+	want, _ := instance.ParseConnNameWithDomainName(realConnName, dnsName)
+
+	client, cleanup, err := mock.NewSQLAdminService(
+		context.Background(),
+		mock.ResolveConnectSettingsSuccess(dnsName+".", "uscentral", realConnName, 1),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer cleanup()
+
+	r := dnsInstanceConnectionNameResolver{
+		dnsResolver: &fakeResolver{},
+		client:      client,
+	}
+	got, err := r.Resolve(context.Background(), dnsName)
+	if err != nil {
+		t.Fatal("got error", err)
+	}
+	if got != want {
+		t.Fatal("Got", got, "Want", want)
+	}
+}
+
 func TestDNSInstanceNameResolver_Lookup_Success_CnamePSC(t *testing.T) {
 	dnsName := "db.example.com"
 	cnameTarget := "0123456789ab.fedcba9876543.europe-north2.sql-psc.goog"
@@ -155,11 +183,12 @@ func TestDNSInstanceNameResolver_Lookup_Success_CnamePSC(t *testing.T) {
 
 func TestDNSInstanceNameResolver_Lookup_Fails_InvalidPattern(t *testing.T) {
 	invalidDNSNames := []string{
-		"0123456789ab.fedcba9876543.europe-north2.sql-psc.goog.com", // wrong suffix domain
-		"0123456789ag.fedcba9876543.europe-north2.sql-psc.goog",     // non-hex char 'g' in hash
-		"0123456789a.fedcba9876543.europe-north2.sql-psc.goog",      // wrong hash length (11)
-		"0123456789abc.fedcba9876543.europe-north2.sql-psc.goog",    // wrong hash length (13)
-		"0123456789ab.fedcba9876543.europenorth2.sql-psc.goog",      // region has no hyphen
+		"0123456789ab.fedcba9876543.europe-north2.sql-psc.goog.com",   // wrong suffix domain
+		"0123456789ab.fedcba9876543.europe-north2.sql-psc.goog.other", // wrong suffix
+		"0123456789ab..europe-north2.sql-psc.goog",                    // empty project label
+		"-abc.def.ghi.sql.goog",                                       // label starts with hyphen
+		"abc-.def.ghi.sql.goog",                                       // label ends with hyphen
+		"abc.def.ghi.sql-other.goog",                                  // invalid suffix type
 	}
 
 	for _, dnsName := range invalidDNSNames {
diff --git a/monitored_cache_test.go b/monitored_cache_test.go
index 09e1929b..25a1af0b 100644
--- a/monitored_cache_test.go
+++ b/monitored_cache_test.go
@@ -124,3 +124,43 @@ func TestMonitoredCache_Close(t *testing.T) {
 	}
 
 }
+
+func TestMonitoredCache_OptimizationForImmutableNames(t *testing.T) {
+	tcs := []struct {
+		desc       string
+		domainName string
+		wantTicker bool
+	}{
+		{
+			desc:       "custom DNS name",
+			domainName: "db.example.com",
+			wantTicker: true,
+		},
+		{
+			desc:       "immutable instance DNS name",
+			domainName: "0123456789ab.fedcba9876543.us-central1.sql-psc.goog",
+			wantTicker: false,
+		},
+		{
+			desc:       "mutable global instance DNS name",
+			domainName: "0123456789ab.fedcba9876543.global.sql-psc.goog",
+			wantTicker: true,
+		},
+	}
+
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			cn, err := instance.ParseConnNameWithDomainName("my-project:my-region:my-instance", tc.domainName)
+			if err != nil {
+				t.Fatalf("ParseConnNameWithDomainName failed: %v", err)
+			}
+			c := newMonitoredCache(&spyConnectionInfoCache{}, cn, 10*time.Millisecond, nil, &testLog{t: t})
+			defer c.Close()
+
+			hasTicker := c.domainNameTicker != nil
+			if hasTicker != tc.wantTicker {
+				t.Errorf("got ticker = %v, want %v", hasTicker, tc.wantTicker)
+			}
+		})
+	}
+}