SELECT 
  pvgp.group_id, 
  pvgf.purpose, 
  pfv.feature_id, 
  pfv.variant_id, 
  pfv.value, 
  pfv.value_int, 
  pfvd.variant, 
  pfd.description 
FROM 
  cscart_product_variation_group_products as pvgp 
  LEFT JOIN cscart_product_variation_group_features as pvgf ON pvgf.group_id = pvgp.group_id 
  LEFT JOIN cscart_product_features_descriptions pfd ON pfd.feature_id = pvgf.feature_id 
  AND pfd.lang_code = 'en' 
  LEFT JOIN cscart_product_features_values as pfv ON pfv.feature_id = pvgf.feature_id 
  AND pfv.product_id = 89 
  AND pfv.lang_code = 'en' 
  LEFT JOIN cscart_product_feature_variant_descriptions as pfvd ON pfvd.variant_id = pfv.variant_id 
  AND pfvd.lang_code = 'en' 
WHERE 
  pvgp.product_id = 89

Query time 0.00058

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "pvgp",
      "access_type": "ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 100,
      "using_index": true
    },
    "table": {
      "table_name": "pvgf",
      "access_type": "ref",
      "possible_keys": ["idx_group_id"],
      "key": "idx_group_id",
      "key_length": "3",
      "used_key_parts": ["group_id"],
      "ref": ["herbaria_cscart_4_18.pvgp.group_id"],
      "rows": 1,
      "filtered": 100
    },
    "table": {
      "table_name": "pfd",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["feature_id", "lang_code"],
      "ref": ["herbaria_cscart_4_18.pvgf.feature_id", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(pfd.lang_code = 'en' and trigcond(pvgf.feature_id is not null))"
    },
    "table": {
      "table_name": "pfv",
      "access_type": "ref",
      "possible_keys": [
        "PRIMARY",
        "fl",
        "lang_code",
        "product_id",
        "fpl",
        "idx_product_feature_variant_id"
      ],
      "key": "PRIMARY",
      "key_length": "6",
      "used_key_parts": ["feature_id", "product_id"],
      "ref": ["herbaria_cscart_4_18.pvgf.feature_id", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(pfv.lang_code = 'en' and trigcond(pvgf.feature_id is not null))"
    },
    "table": {
      "table_name": "pfvd",
      "access_type": "eq_ref",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "9",
      "used_key_parts": ["variant_id", "lang_code"],
      "ref": ["herbaria_cscart_4_18.pfv.variant_id", "const"],
      "rows": 1,
      "filtered": 100,
      "attached_condition": "trigcond(pfvd.lang_code = 'en' and trigcond(pfv.variant_id is not null))"
    }
  }
}