SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '303f93ecd2b0fe10ff0cf3dea298b34fafdf6204554dd0d440c608e78303be33' 
  AND token = 'KbQua9IUuCxqrLb6SR0TVh/7YId0oWxPm9DM020zbVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}