SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'vi' 
WHERE 
  pfv.variant_id IN (
    70974, 70973, 70975, 71508, 71509, 71511, 
    71510, 71520, 71519, 71518, 71521, 
    74429, 76046, 82407, 82408, 82409, 
    82410, 82411, 82412, 82416, 82417, 
    82418, 83392, 83399, 83400, 83401, 
    83402, 83403, 83404, 83405, 83393, 
    83394, 83395, 83396, 83397, 83398, 
    85227, 85228, 85229, 85230, 85231, 
    85232, 85233, 85234, 85235, 85236, 
    85237, 87190, 87191, 87192
  )

Query time 0.00863

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["variant_id"],
          "rows": 50,
          "filtered": 100,
          "index_condition": "pfv.variant_id in (70974,70973,70975,71508,71509,71511,71510,71520,71519,71518,71521,74429,76046,82407,82408,82409,82410,82411,82412,82416,82417,82418,83392,83399,83400,83401,83402,83403,83404,83405,83393,83394,83395,83396,83397,83398,85227,85228,85229,85230,85231,85232,85233,85234,85235,85236,85237,87190,87191,87192)"
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "ref": ["dev_db.pfv.variant_id", "const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "pfvd.lang_code = 'vi'"
        }
      }
    ]
  }
}