# UNDF: UNDF-2026-000000030
diff --git a/pkg/k8s/slim/k8s/apis/labels/selector.go b/pkg/k8s/slim/k8s/apis/labels/selector.go
index 1234567..abcdef0 100644
--- a/pkg/k8s/slim/k8s/apis/labels/selector.go
+++ b/pkg/k8s/slim/k8s/apis/labels/selector.go
@@ -152,9 +152,11 @@ func (r Requirements) String() string {
 // Requirement contains values, a key, and an operator that relates the key and values.
 // The zero value of Requirement is invalid.
 // Requirement implements both set based match and exact match.
 // Requirement should be initialized via NewRequirement constructor for creating a valid Requirement.
 type Requirement struct {
 	key      string
 	operator selection.Operator
-	// In huge majority of cases we have at most one value here.
-	// It is generally faster to operate on a single-element slice
-	// than on a single-element map, so we have a slice here.
-	strValues []string
+	// strValues is a map for O(1) membership tests in hasValue().
+	// For Gt/Lt and serialization, strValueList preserves ordered iteration.
+	strValues     map[string]struct{}
+	strValueList  []string
 }

@@ -210,7 +212,11 @@ func NewRequirement(key string, op selection.Operator, vals []string, opts ...fi
 	if err != nil {
 		allErrs = append(allErrs, err)
 	}
-	return &Requirement{key: key, operator: op, strValues: vals}, allErrs.ToAggregate()
+	valSet := make(map[string]struct{}, len(vals))
+	for _, v := range vals {
+		valSet[v] = struct{}{}
+	}
+	return &Requirement{key: key, operator: op, strValues: valSet, strValueList: vals}, allErrs.ToAggregate()
 }

@@ -216,7 +222,8 @@ func NewRequirement(key string, op selection.Operator, vals []string, opts ...fi
-func (r *Requirement) hasValue(value string) bool {
-	return slices.Contains(r.strValues, value)
+// hasValue is O(1) via map lookup instead of O(n) slices.Contains.
+func (r *Requirement) hasValue(value string) bool {
+	_, ok := r.strValues[value]
+	return ok
 }

@@ -260,7 +268,7 @@ func (r *Requirement) Matches(ls Labels) bool {
 		if len(r.strValues) != 1 {
 		...
 		}
-		for i := range r.strValues {
-			rValue, err = strconv.ParseInt(r.strValues[i], 10, 64)
+		for _, v := range r.strValueList {
+			rValue, err = strconv.ParseInt(v, 10, 64)
 			...
 		}

@@ -293,8 +301,8 @@ func (r *Requirement) Values() sets.String {
 	ret := sets.String{}
-	for i := range r.strValues {
-		ret.Insert(r.strValues[i])
+	for v := range r.strValues {
+		ret.Insert(v)
 	}
 	return ret
 }

@@ -301,8 +309,7 @@ func (r *Requirement) ValuesUnsorted() []string {
-	ret := make([]string, 0, len(r.strValues))
-	ret = append(ret, r.strValues...)
-	return ret
+	return append([]string(nil), r.strValueList...)
 }

@@ -309,5 +317,5 @@ func (r *Requirement) String() string {
-	return r.strValues
+	return r.strValueList
 }

@@ -320,5 +328,5 @@ func (r Requirement) Equal(x Requirement) bool {
-	return slices.Equal(r.strValues, x.strValues)
+	return slices.Equal(r.strValueList, x.strValueList)
 }