diff --git a/pkg/log/gcp_handler.go b/pkg/log/gcp_handler.go
new file mode 100644
index 0000000..771430d
--- /dev/null
+++ b/pkg/log/gcp_handler.go
@@ -0,0 +1,41 @@
+package log
+
+import (
+	"fmt"
+	"log/slog"
+	"runtime"
+)
+
+func labelsAttr(service, env string) slog.Attr {
+	return slog.Group("logging.googleapis.com/labels",
+		slog.String("app", service),
+		slog.String("env", env),
+	)
+}
+
+// attrReplacerForCloudLogging replaces slog's default attributes for Google Cloud Logging.
+func attrReplacerForCloudLogging(groups []string, attr slog.Attr) slog.Attr {
+	switch attr.Key {
+	case slog.MessageKey:
+		attr.Key = "message"
+	case slog.LevelKey:
+		attr.Key = "severity"
+		// Replace the value of the "severity" attribute with the value of the "level" attribute.
+		level, ok := attr.Value.Any().(slog.Level)
+		if ok {
+			attr.Value = toLogLevel(level)
+		}
+	case slog.SourceKey:
+		attr.Key = "logging.googleapis.com/sourceLocation"
+		// Replace the value of the "source" attribute with the value of the "sourceLocation" attribute.
+		const skip = 7
+		_, file, line, ok := runtime.Caller(skip)
+		if !ok {
+			return attr
+		}
+		v := fmt.Sprintf("%s:%d", file, line)
+		attr.Value = slog.StringValue(v)
+	}
+
+	return attr
+}
diff --git a/pkg/log/log.go b/pkg/log/log.go
index 4fe38ee..4a939e3 100644
--- a/pkg/log/log.go
+++ b/pkg/log/log.go
@@ -2,23 +2,20 @@ package log
 
 import (
 	"context"
-	"fmt"
 	"log/slog"
 	"os"
-	"runtime"
-
-	"cloud.google.com/go/logging"
 )
 
 //nolint:gochecknoglobals
 var (
-	SeverityDefault  = slog.Level(logging.Default)
-	SeverityDebug    = slog.Level(logging.Debug)
-	SeverityInfo     = slog.Level(logging.Info)
-	SeverityNotice   = slog.Level(logging.Notice)
-	SeverityWarning  = slog.Level(logging.Warning)
-	SeverityError    = slog.Level(logging.Error)
-	SeverityCritical = slog.Level(logging.Critical)
+	// Custom severity levels.
+	SeverityDebug    = slog.Level(-1)
+	SeverityInfo     = slog.Level(10)
+	SeverityNotice   = slog.Level(20)
+	SeverityWarning  = slog.Level(30)
+	SeverityError    = slog.Level(40)
+	SeverityCritical = slog.Level(50)
+	SeverityDefault  = slog.Level(SeverityInfo)
 )
 
 // logger is the global logger.
@@ -45,10 +42,7 @@ func newHandler(format, service, env string) slog.Handler {
 			ReplaceAttr: attrReplacerForCloudLogging,
 		})
 		handler.WithAttrs([]slog.Attr{
-			slog.Group("logging.googleapis.com/labels",
-				slog.String("app", service),
-				slog.String("env", env),
-			),
+			labelsAttr(service, env),
 		})
 		return handler
 	case "json":
@@ -74,34 +68,6 @@ func attrReplacerForDefault(groups []string, attr slog.Attr) slog.Attr {
 	return attr
 }
 
-// attrReplacerForCloudLogging replaces slog's default attributes for Google Cloud Logging.
-func attrReplacerForCloudLogging(groups []string, attr slog.Attr) slog.Attr {
-	switch attr.Key {
-	case slog.MessageKey:
-		attr.Key = "message"
-	case slog.LevelKey:
-		attr.Key = "severity"
-		attr.Value = slog.StringValue(logging.Severity(attr.Value.Any().(slog.Level)).String())
-		// Replace the value of the "severity" attribute with the value of the "level" attribute.
-		level, ok := attr.Value.Any().(slog.Level)
-		if ok {
-			attr.Value = toLogLevel(level)
-		}
-	case slog.SourceKey:
-		attr.Key = "logging.googleapis.com/sourceLocation"
-		// Replace the value of the "source" attribute with the value of the "sourceLocation" attribute.
-		const skip = 7
-		_, file, line, ok := runtime.Caller(skip)
-		if !ok {
-			return attr
-		}
-		v := fmt.Sprintf("%s:%d", file, line)
-		attr.Value = slog.StringValue(v)
-	}
-
-	return attr
-}
-
 // toLogLevel converts a slog.Level to a slog.Value.
 func toLogLevel(level slog.Level) slog.Value {
 	ls := "DEFAULT"