SELECT 
  content 
FROM 
  cscart_cp_search_motivation 
WHERE 
  object_type = 'C' 
  AND object_id = 538 
  AND company_id = '1' 
  AND lang_code = 'ru'

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_cp_search_motivation",
          "access_type": "const",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "16",
          "used_key_parts": ["object_type", "object_id", "lang_code", "company_id"],
          "ref": ["const", "const", "const", "const"],
          "rows": 1,
          "filtered": 100
        }
      }
    ]
  }
}