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 (
    70905, 70904, 70903, 70906, 76633, 76632, 
    77120, 77118, 77119, 77121, 77668, 
    77665, 77666, 77667, 81491, 81492, 
    81655, 81656, 81657, 81658, 81659, 
    81660, 81661, 81662, 81663, 81664, 
    81665, 81666, 81667, 81668, 81669, 
    81670, 81671, 81672, 81673, 85392, 
    85393, 86299, 86298, 86297, 87462, 
    87461, 86301, 86300, 87456, 87455, 
    87458, 87457, 87460, 87459
  )

Query time 0.00538

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 (70905,70904,70903,70906,76633,76632,77120,77118,77119,77121,77668,77665,77666,77667,81491,81492,81655,81656,81657,81658,81659,81660,81661,81662,81663,81664,81665,81666,81667,81668,81669,81670,81671,81672,81673,85392,85393,86299,86298,86297,87462,87461,86301,86300,87456,87455,87458,87457,87460,87459)"
        }
      },
      {
        "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'"
        }
      }
    ]
  }
}