diff --git a/bulkerlib/implementations/sql/clickhouse.go b/bulkerlib/implementations/sql/clickhouse.go
index 909d7a6..04a282b 100644
--- a/bulkerlib/implementations/sql/clickhouse.go
+++ b/bulkerlib/implementations/sql/clickhouse.go
@@ -11,6 +11,7 @@ import (
 	"github.com/jitsucom/bulker/jitsubase/errorj"
 	"github.com/jitsucom/bulker/jitsubase/jsoniter"
 	"github.com/jitsucom/bulker/jitsubase/logging"
+	"github.com/jitsucom/bulker/jitsubase/timestamp"
 	types2 "github.com/jitsucom/bulker/jitsubase/types"
 	"github.com/jitsucom/bulker/jitsubase/utils"
 	"github.com/jitsucom/bulker/jitsubase/uuid"
@@ -949,7 +950,7 @@ func convertType(value any, column types.SQLColumn) (any, error) {
 	case "string":
 		switch n := v.(type) {
 		case time.Time:
-			return n.Format("2006-01-02 15:04:05Z"), nil
+			return n.Format(timestamp.JsonISO), nil
 		case int64:
 			return strconv.FormatInt(n, 10), nil
 		case float64:
diff --git a/bulkerlib/implementations/sql/options.go b/bulkerlib/implementations/sql/options.go
index 6e6d988..dec5138 100644
--- a/bulkerlib/implementations/sql/options.go
+++ b/bulkerlib/implementations/sql/options.go
@@ -56,7 +56,7 @@ var (
 
 	MaxColumnsCount = bulker.ImplementationOption[int]{
 		Key:          "maxColumnsCount",
-		DefaultValue: 10000,
+		DefaultValue: 5000,
 		ParseFunc:    utils.ParseInt,
 	}
 
diff --git a/bulkerlib/types/converter.go b/bulkerlib/types/converter.go
index 85f3706..7936705 100644
--- a/bulkerlib/types/converter.go
+++ b/bulkerlib/types/converter.go
@@ -208,7 +208,7 @@ func anyToBoolean(v any) (any, error) {
 func timestampToString(v any) (any, error) {
 	switch t := v.(type) {
 	case time.Time:
-		return t.Format(timestamp.Layout), nil
+		return t.Format(timestamp.JsonISO), nil
 	case string:
 		return t, nil
 	default: