diff --git a/internal/captcha/db.go b/internal/captcha/db.go
index 14df7f8..7342cbf 100644
--- a/internal/captcha/db.go
+++ b/internal/captcha/db.go
@@ -17,6 +17,7 @@ type ICaptchaDB interface {
 	Image(id ID) (*image.Image, error)
 	Solve(id ID, answer Answer) (bool, error)
 	IsSolved(id ID) bool
+	GetExpireInterval() time.Duration
 }
 
 type CaptchaDB struct {
@@ -102,3 +103,7 @@ func (cdb *CaptchaDB) IsSolved(id ID) (bool, error) {
 	}
 	return false, errorNotFound
 }
+
+func (cdb *CaptchaDB) GetExpireInterval() time.Duration {
+	return cdb.ExpireInterval
+}