SELECT 
  * 
FROM 
  cscart_abt__ut2_settings 
WHERE 
  lang_code = 'ru' 
  AND storefront_id = 4

Query time 0.00121

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_abt__ut2_settings",
      "access_type": "ALL",
      "rows": 4007,
      "filtered": 100,
      "attached_condition": "cscart_abt__ut2_settings.storefront_id = 4 and cscart_abt__ut2_settings.lang_code = 'ru'"
    }
  }
}