SELECT 
  * 
FROM 
  cscart_abt__ut2_less_settings 
WHERE 
  style = 'Dark_Blue.less'

Query time 0.00012

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_abt__ut2_less_settings",
      "access_type": "ALL",
      "rows": 1,
      "filtered": 100,
      "attached_condition": "cscart_abt__ut2_less_settings.style = 'Dark_Blue.less'"
    }
  }
}