SELECT 
  p.*, 
  pd.* 
FROM 
  cscart_ab__emd_patterns AS p 
  INNER JOIN cscart_ab__emd_patterns_descriptions AS pd ON p.pattern_id = pd.pattern_id 
  AND pd.lang_code = 'ru' 
WHERE 
  p.company_id = 4

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "p",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "p.company_id = 4"
    },
    "table": {
      "table_name": "pd",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["pattern_id", "lang_code"],
      "ref": ["devmotorsbay.p.pattern_id", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "pd.lang_code = 'ru'"
    }
  }
}